Marble Blondies

Marble Blondies with Brownie Filling

There’s something magical about blondies and brownies coming together, the rich chocolate swirls, the golden chewy edges, and that gooey center that melts in your mouth. These Marble Blondies are one of my favorite bakes because they combine the best of both worlds: a buttery vanilla blondie base and a fudgy brownie layer, all marbled together into one irresistible bite. I love how my kitchen fills with the sweet scent of vanilla and cocoa while they bake; it’s pure comfort in dessert form.

Let’s make these delicious Marble Blondies together. They’re surprisingly simple to prepare, and I’ll walk you through each step so they come out perfectly swirled, soft, and full of flavor every single time.

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Why You’ll Love These Marble Blondies

If you can’t decide between a blondie or a brownie, this recipe gives you the best of both worlds. Each bite is a swirl of buttery vanilla blondie and deep, chocolatey brownie, loaded with chunks of white and milk chocolate that melt into sweet pockets of bliss. They’re easy to make, perfectly indulgent, and look stunning straight out of the pan.

Ingredients & Their Purpose

For the Blondie Layer

• ½ cup unsalted butter (melted) – Creates a rich, buttery base and helps give that classic chewy blondie texture.

• 1 cup brown sugar – Adds moisture, chewiness, and a warm caramel flavor.

• 2 eggs (room temperature) – Bind the batter and create structure while keeping it soft.

• 1 tbsp vanilla extract – Deepens the flavor and enhances the sweetness of the brown sugar.

• 1 cup all-purpose flour – Provides the structure that holds the blondie together.

• ¼ tsp baking powder – Adds a slight lift to prevent the blondies from being too dense.

• ½ tsp salt – Balances sweetness and brings out the buttery flavor.

• 1 White Chocolate Tony’s Chocolonely bar (or ¾ cup white chocolate chips) – Adds creamy sweetness and rich texture. Reserve a few pieces for topping before baking.

For the Brownie Swirl

• 4 tbsp butter (melted) – Adds moisture and richness to the fudgy brownie layer.

• ¼ cup granulated sugar – Sweetens and helps achieve that glossy brownie texture.

• 1 egg (room temperature) – Bind the batter and create structure while keeping it soft.

• ¼ cup cocoa powder – Brings deep chocolate flavor and color contrast to the blondie.

• ¼ cup all-purpose flour – Binds the brownie mixture and keeps it dense and fudgy.

• ¼ tsp salt – Enhances chocolate flavor and balances sweetness.

• 1 Milk Chocolate Tony’s Chocolonely bar (or ¾ cup milk chocolate chips) – Adds creamy, melty chocolate chunks throughout. Reserve a few for topping.

👩‍🍳 Step-by-Step Instructions

1. Prep Your Pan

Preheat your oven to 350°F (175°C). Line a 9x9-inch baking pan with parchment paper, leaving some overhang for easy removal later.

2. Make the Brownie Batter

In a medium bowl, combine melted butter and granulated sugar, mixing until smooth.
Add one egg and stir until fully combined.
Whisk in cocoa powder, flour, and salt, then fold in the milk chocolate chunks.
Set aside while you prepare the blondie layer.

Pro Tip: Let the melted butter cool slightly before adding the egg to prevent scrambling.

3. Make the Blondie Batter

In a large bowl, mix together melted butter and brown sugar with a spatula until combined and glossy.
Add the eggs and vanilla extract, mixing until just incorporated.
Fold in flour, baking powder, and salt until no streaks of flour remain — be careful not to overmix.
Finally, fold in the white chocolate chunks.

Baker’s Note: Overmixing can make blondies dense instead of chewy, so stop as soon as the flour disappears!

4. Assemble the Marble Layers

Spread two-thirds of the blondie batter evenly into the bottom of your prepared pan.
Pour the brownie batter over the top and spread it gently to cover.
Then, scoop the remaining blondie batter over the top in spoonfuls.
Use a butter knife to swirl the two batters together for a marbled effect — don’t over-swirl or the layers will blend completely.

5. Bake

Bake for 30–35 minutes, or until the edges are golden brown and the center is set but slightly soft.
Allow the blondies to cool completely on a wire rack before slicing.

Tip: They’ll continue to set as they cool, so avoid overbaking for that gooey center!

💡 Helpful Tips

• Use room-temperature eggs – they mix more evenly and create a smoother batter.

• Don’t overmix either batter – it can cause tough or dry blondies.

• For extra shine, press reserved chocolate chunks into the top before baking.

• Want them extra fudgy? Bake for 28–30 minutes and let cool fully before cutting.

• Clean slices: Use a warm, sharp knife and wipe between cuts.

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Troubleshooting Guide

Problem	Likely Cause	Easy Fix
Blondies came out dry	Overbaked or too much flour	Bake 2–3 minutes less next time, or spoon & level flour (don’t pack).
Layers didn’t swirl nicely	Overmixed during marbling	Use a light hand and a butter knife for gentle swirls.
Center too gooey	Underbaked	Bake an extra 3–5 minutes and let cool fully before slicing.
Chocolate sank to the bottom	Batter too warm or chunks too heavy	Let batter rest 5 minutes before baking and press some chunks into the top.

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Final Thoughts

These marble blondies are the perfect blend of soft, chewy blondie and rich, fudgy brownie. Every bite has a swirl of vanilla and chocolate magic. They’re simple to make but look bakery-special, and they’re guaranteed to impress anyone lucky enough to snag a piece. If you make these, feel free to share how you liked them in the comments below! Happy baking :)

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Marble Blondies

Yield: 16

Author: Jaegar Desjardin

Prep time: 15 MinCook time: 30 MinTotal time: 45 Min

These Marble Blondies are the perfect mix of chewy blondies and fudgy brownies, swirled together with rich milk and white chocolate chunks in every bite.

Ingredients

Blondie Filling

• ½ cup unsalted butter (melted)
• 1 cup brown sugar
• 2 eggs (room temperature)
• 1 tbsp vanilla extract
• 1 cup of all-purpose flour
• ¼ tsp of baking powder
• ½ tsp salt
• 1 White Chocolate Tony's Chocolonely bar, broken into chunks (or 3/4 cup of white chocolate chips), reserve a few chunks for topping.

Brownie Filling

• 4 tablespoons butter (melted)
• 1/4 cup granulated sugar
• 1/4 cup baking cocoa powder
• 1/4 cup all-purpose flour
• 1/4 tsp salt
• 1 Milk Chocolate Tony's Chocolonely bar, broken into chunks (or 3/4 cup of chocolate chips), reserve a few chunks for topping.

Instructions

1. Preheat the oven to 350 degrees and line a 9x9 pan with parchment paper.
2. For the brownie batter. Melt the 4 tablespoons of butter and allow it to cool slightly. When ready, add to a medium bowl with the granulated sugar and mix until combined. Next, add the egg, mixing until combined.
3. Then add the cocoa powder, all-purpose flour, and salt, and mix until combined. Finally, fold in Tony's Chocolonely milk chocolate chunks, then set aside.
4. For the blondie base: Melt the ½ cup of butter and allow it to cool slightly.
5. Add the melted butter and brown sugar to a large bowl and mix with a spatula until combined. Next, add the eggs and vanilla extract and mix until just combined.
6. Use a spatula to scrape down the sides and add the flour, baking powder, and salt. Fold the ingredients together until there are no clumps of flour without overmixing.
7. Then, fold in fold in Tony's Chocolonely white chocolate chunks
8. Add 2/3 of the blondie mixture into the bottom of the prepared pan. Then add the brownie mixture and spread it in an even layer over the blondie base. Next, using a medium cookie scoop, scoop the remainder of the brownie mixture over the top and use a butter knife to create swirls with the brownie mixture.
9. Bake for 30-35 minutes or until the edges are golden brown.
10. Allow to cool on a wire rack and enjoy!

Equipment

1. 9x9 baking pan
2. Parchment paper
3. Wire rack
4. Spatula
5. Bowls