Tangy Rhubarb Custard Blondies

Prepare to be enchanted by these delightful Rhubarb and Custard Blondies, a truly irresistible treat that promises to keep you reaching for another slice. Imagine soft, buttery squares, generously crowned with a vibrant rhubarb compote, a luscious layer of creamy custard, and an elegant drizzle of white chocolate. These aren’t just any blondies; they are a symphony of textures and flavors designed to excite your palate.

Each bite offers a perfect contrast: a wonderfully soft and gooey center that melts in your mouth, complemented by delightfully crispy and chewy edges. Whether you’re planning a casual get-together, a family celebration, or simply craving a moment of sweet indulgence, these blondies are the ideal dessert to share with loved ones. What’s more, this recipe is incredibly straightforward, coming together quickly without the need for any specialized kitchen equipment, making it accessible for bakers of all skill levels.

Close-up shot of three delicious rhubarb and custard blondies stacked on top of each other, showcasing their layers and white chocolate drizzle.

Why You’ll Fall in Love with These Rhubarb and Custard Blondies

There are countless reasons why these Rhubarb and Custard Blondies are destined to become a firm favorite in your baking repertoire. This recipe celebrates one of the most classic and cherished British flavor pairings: the delicate tartness of rhubarb perfectly balanced by the sweet, comforting embrace of velvety smooth custard. It’s a combination that has charmed palates for generations, and this blondie rendition elevates it to new heights, offering a truly unique and memorable dessert experience.

Beyond the exquisite flavor, the textural interplay is simply divine. The tender, slightly tangy rhubarb compote provides a delightful counterpoint to the rich, dense, and fudgy blondie base. Imagine biting into that soft, chewy interior, studded with chunks of sweet white chocolate, then discovering the creamy custard layer and the bright burst of rhubarb. It’s a truly dynamic experience for your taste buds, with each element contributing to an overall sense of indulgence and satisfaction that will leave you craving more.

Furthermore, these blondies are incredibly versatile. They make an excellent dessert for dinner parties, a much-loved addition to bake sales, or a comforting treat for a quiet afternoon tea. Their robust yet delicate flavors make them suitable for almost any occasion. The striking marble pattern created by swirling the compote and custard into the batter also makes them visually stunning, sure to impress anyone you serve them to, even before the first bite. And despite their sophisticated appearance and gourmet taste, the preparation process is surprisingly simple. You won’t spend hours in the kitchen, making them perfect for those moments when a quick, yet utterly delicious, sweet fix is in order without the fuss of a complicated cake. Plus, with simple pantry staples, you’re likely only a few ingredients away from baking bliss.

This recipe offers a unique twist on traditional blondies, infusing them with a nostalgic charm that evokes memories of homemade custard and fresh fruit crumbles. It’s a testament to how simple ingredients, thoughtfully combined, can create something truly extraordinary. Whether you’re a seasoned baker or a novice in the kitchen, these blondies are designed for success, delivering consistent, mouth-watering results every time. Get ready to bake a batch that will have everyone asking for the recipe and coming back for seconds!

Overhead close-up of rhubarb and custard blondies neatly cut into sixteen perfect squares, ready to be served on a rustic wooden board.

Essential Ingredients and Smart Substitutions for Perfect Blondies

Crafting these amazing Rhubarb and Custard Blondies requires a selection of readily available ingredients, many of which you likely already have in your pantry. Let’s delve into the core components and explore some helpful tips and substitution ideas to ensure your blondies turn out perfectly every time. Understanding the role each ingredient plays will empower you to make informed choices and, if necessary, smart substitutions without compromising on flavor or texture.

Overhead shot showcasing all the fresh and dry ingredients laid out for making rhubarb and custard blondies, including butter, sugars, eggs, rhubarb, and white chocolate.

Rhubarb: The Star of the Show
For the freshest and most vibrant flavor, I highly recommend using fresh rhubarb, especially when it’s in season. Its natural tartness provides a crucial balance to the sweetness of the blondie and custard, preventing the dessert from being overly cloying. When preparing fresh rhubarb, simply wash it thoroughly and chop it into appropriate sizes for the compote. If fresh rhubarb isn’t available, don’t worry! Frozen rhubarb can be used directly without thawing, or even canned rhubarb will work effectively as a substitute. If opting for canned rhubarb, ensure you drain it thoroughly to prevent excess moisture from making your compote watery. Regardless of the type, rhubarb almost always benefits from a touch of sugar to temper its inherent tartness; adjust to your personal taste. Any leftover rhubarb compote can be a delicious addition to breakfast yogurt, oatmeal, or even transformed into a vibrant Strawberry Rhubarb Preserve, extending its delightful flavor beyond these blondies.

Custard: Double the Delight
This recipe ingeniously utilizes two forms of custard to maximize flavor and texture, creating a truly multi-layered experience. Powdered custard is incorporated directly into the blondie batter, partially replacing a portion of the flour. This addition is key to achieving that distinctive, rich, and slightly buttery taste that sets these blondies apart from a typical blondie, while also contributing to their tender crumb. A ready-made custard is then used as a luscious topping, creating a creamy, smooth layer that perfectly complements the tart rhubarb. However, for simplicity or if you only have one type on hand, you can certainly use only powdered custard for both the batter and the topping. Refer to the detailed recipe notes for specific guidance on how to prepare the topping from custard powder to achieve the desired consistency.

White Chocolate: Sweet Chunks of Joy
You’ll need approximately 200-250 grams of white chocolate in total for this recipe. I find that a good quality bar of white chocolate, roughly chopped into small chunks, works best for an appealing textural contrast and a rich, creamy flavor throughout the blondies. These chunky pieces melt slightly during baking, creating inviting pockets of delightful sweetness that burst with flavor. Alternatively, white chocolate chips, buttons, or wafers are perfectly acceptable and can save you a step in preparation. Just ensure you’re using a quality white chocolate that you enjoy eating on its own.

Sugar: The Sweet Foundation
This recipe calls for a blend of two essential sugars: caster sugar (or regular granulated white sugar) and soft light brown sugar. While you could technically use just one type, combining them yields a superior result that significantly impacts both flavor and texture. Brown sugar is a game-changer for blondies; it imparts a wonderful, mellow, and slightly caramel-like depth of flavor to the blondies, which beautifully complements the bright rhubarb and creamy custard. Crucially, it also helps maintain the blondies’ signature soft, moist, and wonderfully fudgy texture due to its higher moisture content. Caster sugar, on the other hand, provides the necessary sweetness and contributes to the slight crispness of the edges, creating a perfectly balanced flavor profile and irresistible chew.

Eggs: The Binding Agent
Eggs play a vital role in providing structure, moisture, and richness to your blondies. They act as a binding agent, holding the batter together, and contribute to the rich, golden hue and delicious flavor. I’ve successfully tested this recipe using either three medium eggs or two large eggs, and both options yield excellent results. Feel free to use whichever size you have on hand, ensuring they are at room temperature for optimal mixing and emulsification with the other ingredients. Room temperature eggs combine more smoothly with butter and sugar, leading to a more homogenous and airier batter.

Flour & Baking Powder: Structure and Lift
Plain, all-purpose flour provides the primary structure for the blondies, giving them body and chew. A small amount of baking powder is included to ensure a slight lift, preventing the blondies from being too dense, but without making them overly cake-like. The goal is a dense, fudgy texture, not a light and airy cake, so the amount of leavening is carefully balanced.

Vanilla Extract: Aromatic Enhancement
A good quality vanilla extract is essential for enhancing the overall flavor profile, adding warmth, depth, and a hint of sweetness that rounds out the flavors of the blondie base, complements the fruit, and pairs beautifully with the custard notes. Don’t skimp on this ingredient; pure vanilla extract makes a noticeable difference in the final taste.

Side close-up of a plate filled with freshly cut rhubarb blondie squares, with a hand reaching to take a piece, highlighting their irresistible nature.

Step-by-Step Guide to Crafting Irresistible Rhubarb and Custard Blondies

Making these glorious blondies is a surprisingly simple process, and the results are incredibly rewarding, even for those new to baking. For a quick visual guide, you can refer to this Instagram Reel which showcases just how easy it is to bring these delightful treats to life!

1. Prepare Your Rhubarb Compote and Custard Topping

Begin by preparing the star components of your topping. If you’re using fresh rhubarb, wash it thoroughly, trim the fibrous ends, and chop it into small, manageable pieces, roughly 2-3 cm long. Place these rhubarb chunks into a wide saucepan along with the specified amount of caster sugar and two tablespoons of water. Cook this mixture over medium heat, stirring frequently, until the rhubarb softens, breaks down, and transforms into a thick, glistening, jammy compote. This process usually takes about 10 minutes. For an even more vibrant appearance that makes the blondies pop, feel free to add a few drops of pink food coloring to intensify the rhubarb’s natural hue. Once cooked, set the compote aside to cool completely, as you don’t want to add hot compote to your batter.

If you’ve opted to use only powdered custard throughout the recipe, this is the stage to prepare your custard topping. Follow the package directions for a thick and creamy custard, ensuring it’s dense enough to dollop. You’ll need approximately 4-5 tablespoons of prepared custard for the topping. Allow it to cool thoroughly before proceeding to the assembly stage.

For those who prefer a different textural experience with rhubarb, you might consider a variation where whole chunks of rhubarb are placed directly on top of the batter, as seen in this inspiring recipe for Rhubarb and White Chocolate Blondies from Hummingbird High. However, for this specific recipe, the jammy compote is key to achieving the beautiful marbled effect and ensuring an integrated, consistent flavor throughout the blondie.

Top view close-up of a bowl filled with vibrant, homemade rhubarb compote, cooked down to a jammy consistency, ready for the blondie topping.

2. Melt the Butter and Sugars for the Blondie Base

In a medium saucepan, combine the butter and both types of sugar (light brown soft sugar and caster sugar). Place the pan over a low heat and allow the butter and sugars to melt together gently. Stir continuously with a rubber spatula or wooden spoon until you achieve a thick, smooth, and glossy mixture. This step is crucial for developing the characteristic dense, fudgy texture of the blondies, as it creates a stable base. Once melted and thoroughly combined, immediately remove the mixture from the heat and set it aside to cool for about 10 minutes. It’s important that the mixture is not too hot when you add the eggs in the next step, as residual heat can cause the eggs to scramble, leading to a lumpy and undesirable batter texture.

Top view of separate bowls, one containing the golden melted butter and sugar mixture, and another with whisked eggs, at room temperature and ready to be combined.
Overhead shot of a person gently mixing room temperature eggs into the cooled butter and sugar batter in a large mixing bowl.

3. Combine Wet and Dry Ingredients for the Batter

While the butter-sugar mixture cools, prepare your dry ingredients. In a large mixing bowl, sift together the plain all-purpose flour, custard powder, and baking powder. Sifting these ingredients together helps to aerate them, preventing any lumps in the final batter and ensuring a lighter, more uniform texture. Once the butter-sugar mixture has cooled sufficiently (it should be warm but not hot), beat the eggs into it vigorously until they are well combined and the mixture has a slightly lighter, creamy consistency. Next, gradually add the sifted dry ingredients to the wet mixture. Fold them in gently using a rubber spatula; be careful not to overmix, as excessive mixing develops gluten, which can lead to tough, cakey blondies instead of the desired fudgy texture. Stir just until no dry streaks of flour remain. Finally, stir in the vanilla extract and then fold in 150g of your chopped white chocolate chunks or chips. This batter should be thick, glossy, and rich.

Top view of a person stirring dry ingredients like flour, custard powder, and baking powder into the prepared blondie cake batter in a mixing bowl.
Top view of a bowl containing thick, golden blondie cake batter, with generous white chocolate chunks folded in, ready for assembly.

4. Assemble and Swirl for a Beautiful Finish

Preheat your oven to 180°C (160°C fan/350°F). Prepare your chosen baking tin (an 8×8 inch square tin is highly recommended for optimal fudgy results) by lightly buttering it and then lining it with baking parchment. Ensure the parchment paper leaves an overhang on all sides; this thoughtful detail will make it incredibly easy to lift the entire slab of cooled blondies out of the pan later. Pour the thick, prepared blondie batter evenly into the lined baking tin, spreading it gently with a spatula to ensure a smooth, level top. Now comes the artistic part: using a teaspoon, carefully dollop spoonfuls of the cooled rhubarb compote and the prepared custard topping randomly over the surface of the batter. Take a cocktail stick, skewer, or even the tip of a knife and gently swirl through the dollops, creating a beautiful, elegant marbled pattern. Be careful not to overmix the swirls; a few gentle passes are enough to create an appealing design without fully incorporating the toppings into the batter.

Top view of a person carefully adding dollops of vibrant rhubarb compote onto the smooth blondie batter spread evenly in a baking tin.
Top view of blondie batter beautifully topped with artful swirls of rhubarb compote and creamy custard, creating a stunning marble effect, ready for the oven.

5. Bake to Perfection and Cool Patiently for Optimal Fudginess

Place your baking tin in the preheated oven. For an 8×8 inch baking tin, bake for approximately 45-50 minutes. You’ll know they’re ready when the edges begin to pull away slightly from the sides of the tin, and the center appears mostly set but still slightly soft and jiggly. For that signature fudgy and gooey texture, a toothpick inserted into the middle should not come out completely clean; it should have some moist crumbs attached. Remember, just like brownies, these blondies will continue to “cook” and set as they cool on the countertop, so don’t be tempted to overbake them! Overbaking is the number one cause of dry, cakey blondies.

If you prefer a more cake-like texture, simply extend the baking time by an additional 5-10 minutes. Keep a close eye on them during this extended period to prevent overbrowning. If the top starts to brown too quickly, loosely tent the tin with aluminum foil to protect it and allow the interior to cook through.

Should you use a larger, shallower baking pan, such as a rectangular 20cm x 30cm (8″ x 12″) tin, the baking time will naturally be shorter due to the increased surface area. For a fudgy consistency in a larger tin, aim for 35-40 minutes. For a more cakey finish, add another 5-10 minutes to that time. Always use the visual cues and the toothpick test as your ultimate guide, as oven temperatures can vary.

Once baked, carefully remove the blondies from the oven. This next step is absolutely crucial for achieving the perfect texture: allow them to cool completely in the tin on a wire rack. Patience is key here. Once cooled to room temperature, you can optionally drizzle them with the remaining melted white chocolate for an extra touch of decadence and visual appeal. Then, transfer the entire tin to the fridge for a minimum of 2 hours, or even better, overnight. This prolonged cooling and chilling period allows the blondies to properly set, firming up to that delightful fudgy consistency that makes them so irresistible. Trying to slice them while warm will likely result in a crumbly, messy outcome, as the structure won’t have fully set. Embrace the wait for truly perfect blondies!

Top view close-up of a single slice of rhubarb and custard blondie bar, highlighting its distinct layers of creamy custard, rhubarb compote, and white chocolate chunks in a fudgy base.

Essential Tips for Blondie Perfection

Achieving the perfect gooey, fudgy blondie every time is easy with these insider tips:

  • Room Temperature Ingredients are Non-Negotiable: Ensure your eggs and butter are at room temperature. This is vital for proper emulsification, leading to a smoother batter, better incorporation of ingredients, and ultimately, a more consistent and tender texture in your baked blondies.
  • Do Not Overmix the Batter: After adding the dry ingredients to the wet mixture, mix just until no visible streaks of flour remain. Overmixing develops gluten, which can make your blondies tough and chewy in an undesirable way, rather than deliciously fudgy and soft.
  • Cool the Melted Butter-Sugar Mixture: As highlighted in the steps, letting the melted butter and sugar cool slightly before incorporating the eggs is paramount. Adding eggs to a hot mixture will cook them prematurely, resulting in a lumpy, unpleasant batter. Patience here ensures a smooth, cohesive base.
  • Master the Toothpick Test: For truly fudgy blondies, the toothpick inserted into the center should come out with moist crumbs attached, not completely clean. If it’s totally wet with raw batter, they need more time. If it’s bone dry, they are unfortunately overbaked. Trust the moist crumb!
  • Patience is Key for Cooling and Setting: Resist the irresistible urge to cut into warm blondies. Chilling is absolutely essential for them to set properly and develop their signature dense, fudgy texture. This cold setting also makes them much easier to slice cleanly into perfect squares without falling apart.
  • Line Your Baking Pan Effectively: Always line your baking tin with parchment paper, ensuring there’s an overhang on the sides. This simple trick makes lifting the entire slab of blondies out of the pan incredibly easy once they’re cool and set, allowing you to cut beautiful, clean squares with minimal fuss.

Serving Your Delicious Rhubarb and Custard Blondies

These Rhubarb and Custard Blondies are undeniably a showstopper on their own, boasting rich flavors and delightful textures. However, a few thoughtful additions and serving ideas can elevate the experience even further, turning a simple treat into an unforgettable dessert.

For the best texture and flavor, serve them at room temperature or slightly chilled after their essential time in the fridge. A light dusting of powdered sugar just before serving adds a touch of elegance and visual appeal. For a truly indulgent dessert experience, pair a gently warmed blondie slice with a generous scoop of high-quality vanilla bean ice cream. The warmth of the blondie allows the ice cream to melt slightly, creating a luscious, creamy sauce that perfectly complements the fudgy base and the tart fruit. Alternatively, a dollop of extra ready-made custard or a swirl of freshly whipped cream would also be a fantastic accompaniment, playing into the classic rhubarb and custard theme with added luxury.

Beyond being a decadent dessert, these blondies are also incredibly versatile. They are perfect for packing into lunchboxes as a special treat, bringing to picnics, or serving at potlucks where they are sure to be a crowd-pleaser. Their sturdy, sliceable nature makes them an excellent grab-and-go snack for satisfying any sweet craving throughout the day. Consider serving them with a hot cup of tea or coffee for a comforting afternoon pick-me-up. No matter how you choose to enjoy them, these blondies promise a moment of pure, unadulterated bliss.

Storing and Freezing Your Rhubarb and Custard Blondies

Proper storage is essential to keeping your delicious Rhubarb and Custard Blondies fresh, fudgy, and flavorful for as long as possible. Given the custard and fruit topping, refrigeration is generally recommended for optimal quality and safety.

Refrigerator Storage: Store any leftover Rhubarb and Custard Blondies in an airtight container in the refrigerator for up to 3-4 days. The cool temperature helps maintain their delightful fudgy texture and ensures that the rhubarb compote and custard topping remain fresh and vibrant. Bringing them to room temperature for about 15-20 minutes before serving can enhance their softness, though many find them equally delicious chilled.

Freezing for Longer Enjoyment: These blondies freeze exceptionally well, making them perfect for meal prepping desserts, preparing treats in advance, or simply saving a batch for a future craving. To freeze, ensure the blondies are completely cool and fully set from their refrigeration period. It’s best to cut them into individual slices first. Wrap each slice tightly in cling film or plastic wrap, ensuring no air can get in, then place them in a freezer-friendly airtight container or a heavy-duty freezer bag. They can be safely stored in the freezer for up to 3 months without significant loss of quality. When you’re ready to enjoy them, simply defrost them overnight in the refrigerator, or for a quicker thaw, leave individual slices at room temperature for a couple of hours. You can enjoy them chilled, or gently warm them in the microwave for a few seconds for a wonderfully soft, gooey experience that tastes freshly baked.

Straight-ahead super close-up of a square slice of rhubarb blondie cake with a bite taken out, showing the gooey interior, white chocolate chunks, and marbled topping.

Frequently Asked Questions About Rhubarb and Custard Blondies

Here are answers to some common questions about making, customizing, and troubleshooting these delicious blondies, ensuring your baking experience is as smooth and successful as possible:

Q: I’m not a fan of rhubarb, or I don’t have any. Can I use anything else instead?
A: Absolutely! The beauty of this recipe lies in its adaptability and the ability to customize it to your preferences or what you have on hand. While rhubarb offers a unique and lovely tartness, you can certainly substitute it with other fruits that have a similar tangy profile, which beautifully balances the sweetness of the blondie base and creamy custard. Excellent choices include fresh strawberries, cranberries, quinces, raspberries, or sour cherries. Simply prepare these fruits into a compote similar to the rhubarb. You could even use a favorite fruit jam (store-bought or homemade) in place of the homemade rhubarb compote for an even quicker preparation method. If you’re looking for other non-fruit blondie ideas, be sure to explore my popular Chocolate Chip Walnut Blondies or the ever-popular, reader-favorite Biscoff White Chocolate Blondies for different flavor profiles.

Q: Can I use a different size baking tin than specified in the recipe?
A: Yes, you certainly can use a different size baking tin! I’ve tested this recipe successfully in various sizes, including an 8″ x 8″ square baking tin (which is my preferred size for the fudgiest results and most consistent bake), an 8″ x 12″ rectangular tin, and even a 9″ round baking tin. The main consideration when changing tin sizes is the adjustment of the baking time. A larger, shallower tin will naturally require a shorter baking time because the batter is spread thinner. Conversely, a smaller, deeper tin will need a longer baking duration. Always use the visual cues (edges pulling away, center mostly set) and the essential toothpick test as your primary guides, adjusting the baking duration as needed to achieve your desired texture.

Top view super close-up of beautifully arranged square slices of rhubarb and custard blondies, showing their consistent shape and inviting toppings.

Q: Why do my blondies look under-baked in the middle when I take them out of the oven?
A: This is perfectly normal and, in fact, desirable for achieving that classic fudgy, gooey texture! Blondies, much like their darker counterparts (brownies), are meant to be slightly under-baked when removed from the oven. They continue to “cook” and set as they cool down, a process known as carryover cooking. If you wait until they appear fully set and firm in the oven, they will likely be dry and overbaked once cooled to room temperature. For a perfectly gooey center, aim for a toothpick inserted into the middle to come out with moist crumbs attached, not liquid batter, but not completely dry either. The residual heat will do the rest!

Q: Help, my blondies are not fudgy and are really dry! What went wrong?
A: It sounds like your blondies were likely overbaked, which is the most common culprit for dry, cakey blondies instead of the desired fudgy texture. Baking them for too long causes too much moisture to evaporate, resulting in a crumbly rather than gooey interior. To prevent this in the future, closely adhere to the suggested baking times provided in the recipe, but always prioritize the visual cues and perform the toothpick test diligently. Start checking for doneness a few minutes before the minimum baking time, and remove them from the oven when the edges are set and the center still looks slightly soft with moist crumbs on the toothpick. Remember that every oven can vary, so learning to trust your instincts and the toothpick test is key to consistently achieving that perfect fudgy consistency.

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📖 Rhubarb and Custard Blondies Recipe

Top view of square slices of blondies topped with rhubarb and custard, showcasing the delicious swirl.

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Rhubarb and Custard Blondies

These gooey rhubarb and custard blondies with white chocolate are to die for! Super easy recipe for utterly delicious dessert that you will find hard to resist!
Prep Time15 minutes
Cook Time55 minutes
Course: Dessert
Cuisine: American
Keyword: blondie, blondie bars, custard blondies, rhubarb blondie
Servings: 16 slices
Calories: 250kcal
Author: Anna Wierzbinska (adapted from BBC Good Food Magazine)

Equipment

  • 8′ x 8′ baking tin
  • baking parchment
  • rubber spatula

Ingredients

  • 225 g unsalted butter plus some extra for greasing the tin
  • 200 g light brown soft sugar
  • 100 g caster sugar
  • 150 g plain, all-purpose flour
  • 50 g custard powder
  • ½ teaspoon baking powder
  • 3 medium eggs or 2 large eggs, at room temperature
  • 250 g white chocolate chips (or finely chopped white chocolate bar)
  • 2 teaspoon vanilla extract

For the rhubarb and custard topping:

  • 200 g rhubarb chopped into 3-4 cm pieces
  • 75 g caster sugar
  • 4 tablespoon ready-made custard or prepare from custard powder as per package instructions
Metric – US Customary

Instructions

To make rhubarb and custard topping:

  • Prepare Rhubarb Compote: Place the chopped rhubarb, 75g caster sugar, and 2 tablespoons of water into a wide pan. Cook over medium heat, stirring frequently, for about 10 minutes, or until the rhubarb softens, breaks down, and becomes jammy. Set aside to cool completely. If desired, add a few drops of pink food coloring for a more vibrant color. If using powdered custard for the topping, prepare it now according to package instructions for a thick consistency, and set aside to cool.
  • Melt Butter and Sugars: Preheat your oven to 180°C (160°C fan/350°F). In a medium pan, combine the 225g butter, 200g light brown soft sugar, and 100g caster sugar. Melt them together over low heat, stirring until the mixture is smooth and glossy. Remove from heat and let it cool for about 10 minutes to prevent the eggs from scrambling.
  • Prepare Dry Ingredients and Baking Tin: In a large bowl, sift together the 150g plain all-purpose flour, 50g custard powder, and ½ teaspoon baking powder. Butter your baking tin (e.g., 8×8 inch square) and line it with baking parchment, leaving an overhang on the sides for easy removal.
  • Combine Batter Ingredients: Beat the 3 medium eggs (or 2 large eggs) into the cooled butter and sugar mixture until well combined. Gradually fold in the sifted dry ingredients until a smooth batter forms. Stir in the 2 teaspoons of vanilla extract and then fold in 150g of white chocolate chips (or chopped white chocolate). Pour the batter evenly into the prepared baking tin.
  • Add Toppings and Swirl: Use a teaspoon to dollop spoonfuls of the cooled rhubarb compote and the 4 tablespoons of ready-made custard over the top of the blondie batter. Take a cocktail stick, skewer, or the tip of a knife and gently swirl through the rhubarb and custard dollops to create a beautiful marbled pattern. Do not overmix.
  • Bake and Cool: Bake for 40-50 minutes (for an 8×8 inch tin) or until the edges are set and lightly golden, and the center appears mostly set but still slightly soft. A toothpick inserted should come out with moist crumbs. If the top browns too quickly, cover loosely with kitchen foil. Remove from the oven and let cool completely in the tin on a wire rack. Once at room temperature, transfer the tin to the fridge for a minimum of 2 hours, or ideally overnight, for the blondies to set properly.
  • Finish and Serve: Melt the remaining 100g of white chocolate chips (or chopped white chocolate). Drizzle the melted white chocolate over the thoroughly cooled and set blondies. Once the drizzle has firmed up, cut the blondies into equal squares and serve. Enjoy!

Please note that all my recipes are developed and tested in metric grams. I recommend that you use digital scales for a more accurate result. I have provided a conversion to US customary in the recipe but please note that I haven’t tested using this method.

Notes

  • Vibrant Rhubarb: To intensify the color of your rhubarb compote, you can add a few drops of pink food coloring during cooking for an even more visually appealing blondie.
  • Rhubarb Alternatives: While fresh rhubarb is wonderful, frozen or canned rhubarb can also be used effectively. If using canned, be sure to drain it thoroughly before cooking to prevent excess moisture.
  • Fruit Substitutions: If rhubarb isn’t to your taste or unavailable, feel free to swap it for your favorite jam or other tart fruits like fresh strawberries, raspberries, quince, tart apples, or cranberries.
  • Storage: Store any leftover blondies in an airtight container in the fridge for up to 4 days to maintain their freshness and fudgy texture.
  • Freezing: These blondies freeze beautifully for longer enjoyment. Wrap each individual slice tightly with cling film, then transfer to a freezer-friendly container or bag and freeze for up to 3 months. Thaw overnight in the fridge before enjoying, or gently warm from frozen.

Nutrition

Calories: 250kcal | Carbohydrates: 44g | Protein: 4g | Fat: 7g | Saturated Fat: 4g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 2g | Trans Fat: 1g | Cholesterol: 45mg | Sodium: 70mg | Potassium: 163mg | Fiber: 1g | Sugar: 33g | Vitamin A: 99IU | Vitamin C: 1mg | Calcium: 94mg | Iron: 1mg
Did you make this?Tell me how you like it? Leave a comment or take a picture and tag @anna_wierzbinska on Instagram. I love seeing your take on my recipes!

This post was originally published in February 2020. It has been updated with new photos and improved tips in June 2021 to enhance your baking experience and ensure the best possible results.