Boston Cream Brownies
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This is the ultimate Boston Cream Brownie recipe–fudgy brownies with a layer of homemade vanilla custard and topped with a 2-ingredient chocolate ganache! If you’re looking for a rich, decadent brownie recipe, you’ve found it!
If you’re a fan of Boston Cream Pie, you’re going to love these fudgy brownies. The vanilla custard tops the freshly baked brownies, and then you top the custard with a super simple chocolate ganache layer. Let it chill in the fridge for a couple of hours and then enjoy!
I’m not going to lie to you: if you don’t like rich desserts, this recipe isn’t for you. I have a couple of other simple brownie recipes, such as these old-fashioned fudgy brownies and these sourdough discard brownies that are easy to make (and very good, I might add).
But *this* recipe–these custard-filled Boston cream brownies– are for the decadent dessert lover. The ones who want a luxurious, indulgent treat. If that’s you, you’ve found it. 🙂
Looking for other bars? Try these:
- sourdough millionaire shortbread
- maple pecan blondies
- white chocolate raspberry blondies
- brown butter brownies
Ingredient Notes for Boston Cream Brownies
- cocoa powder – the ingredients call for unsweetened cocoa powder, I’ve also used unsweetened Dutch-processed cocoa powder.
- chocolate chips – you can use half semi-sweet chocolate chips and half milk chocolate chips to enhance the flavor of these brownies
- butter – I always use salted butter. If you only have unsalted butter, add an additional 1/4 teaspoon to the batter.
Step-By-Step Instructions
Start by preheating your oven to 350°F (177°C) and lining a 9×9-inch pan with parchment paper. In a large mixing bowl, whisk together the melted salted butter and chocolate chips until smooth and glossy.
Next, stir in the granulated sugar, eggs, egg yolks, and vanilla extract. The batter should look thick and shiny. Sift in the cocoa powder and flour, and gently fold everything together until fully combined.
Pour the brownie batter into your prepared pan and spread it evenly. Bake for 35 to 40 minutes, or until the edges are set and the center still has a little give. A toothpick should come out with a few moist crumbs. Let the brownies cool completely in the pan while you prepare the custard.
While the brownies cool, start on the vanilla custard layer. In a medium bowl, whisk together the eggs, egg yolks, and cornstarch until smooth and pale. Set this aside.
In a saucepan over medium heat, combine the milk, sugar, salt, and a pinch of cinnamon (optional, but it adds a cozy touch). Whisk the mixture gently until it’s steaming—don’t let it boil.
To temper the eggs (and avoid scrambling them), slowly drizzle about 1 cup of the hot milk mixture into the egg mixture while whisking constantly. Once tempered, pour the egg mixture back into the saucepan with the rest of the milk, whisking the entire time.
Continue cooking over medium heat, whisking constantly, until the custard thickens to a pudding-like consistency—this takes about 3–5 minutes. Remove from heat and stir in the vanilla extract.
Pour the warm custard over the cooled brownie layer, smoothing it out evenly. Chill the pan in the refrigerator for 30 minutes to allow the custard to set.
Once the custard layer is chilled and set, it’s time for the ganache.
Heat the heavy cream in a small saucepan over medium heat until it begins to gently simmer. Pour the hot cream over the chocolate chips in a heat-safe bowl and then stir until smooth and glossy.
Pour the ganache over the custard layer and use a spatula to spread it out evenly. Return the pan to the fridge and chill for at least 2–4 hours, or until everything is fully set and sliceable.
Use a sharp knife to cut clean squares, wiping the blade between slices for neat edges.
Equipment Needed
- 9×9 baking pan – for baking the brownie base
- Parchment paper – to line the pan and ensure easy removal
- Mixing bowls – at least two (one for brownie batter, one for custard)
- Medium saucepan – for heating the milk mixture and making ganache
- Whisk – for mixing batter, tempering eggs, and whisking custard
- Rubber spatula or wooden spoon – to fold ingredients and spread layers
- Fine mesh strainer or sifter – optional, for sifting cocoa powder and flour
- Measuring cups and spoons – for accurate measurements
- Heat-safe bowl – for melting chocolate with hot cream (ganache)
- Offset spatula or butter knife – for spreading custard and ganache evenly
- Sharp knife – for slicing clean brownie squares
Storage
Store leftover brownies in an airtight container in the fridge for up to 5 days.
Boston Cream Brownies
Ingredients
For the Brownie Layer
- 1 cup salted butter melted
- 1 cup semi-sweet chocolate chips
- 2 cups granulated sugar
- 4 large eggs 2 whole eggs + 2 egg yolks
- 1 tablespoon vanilla extract
- ½ cup unsweetened cocoa powder
- 1 cup all-purpose flour
For the Vanilla Custard
- 2 large eggs
- 2 egg yolks
- ¼ cup cornstarch
- 2 cups milk
- ½ cup granulated sugar
- ¼ teaspoon salt
- 1 teaspoon vanilla extract
For the Chocolate Ganache
- 1 cup heavy cream
- 2 cups semi-sweet chocolate chips
Instructions
Make the Brownies
- Preheat oven to 350°F (177°C) and line a 9×9-inch baking pan with parchment paper.
- In a large bowl, whisk together melted butter and chocolate chips until smooth.
- Stir in the sugar, eggs, egg yolks, and vanilla extract until glossy and well combined.
- Sift in the cocoa powder and flour, then gently fold until just incorporated.
- Pour the batter into the prepared pan and bake for 35–40 minutes, or until a toothpick comes out with a few moist crumbs.
- Let the brownies cool completely in the pan.
Prepare the Vanilla Custard
- In a mixing bowl, whisk together the eggs, egg yolks, and cornstarch until smooth. Set aside.
- In a medium saucepan over medium heat, combine the milk, sugar, salt, and a pinch of cinnamon (optional but delicious). Whisk gently until the mixture is steaming but not boiling.
- Carefully scoop out 1 cup of the hot milk mixture and slowly drizzle it into the egg mixture, whisking constantly to temper the eggs and prevent them from scrambling.
- Gradually pour the tempered egg mixture back into the saucepan with the remaining milk, whisking continuously as you add it.
- Cook over medium heat, whisking constantly, until the custard thickens—about 3 to 5 minutes.
- Once thick and pudding-like, remove from heat and stir in the vanilla extract.
- Pour the warm custard over the cooled brownie layer and spread it evenly with a spatula.
- Chill in the refrigerator for at least 30 minutes to set before adding the ganache.
Make the Chocolate Ganache
- In a small saucepan, heat the heavy cream until it just begins to simmer.
- Pour over the chocolate chips in a heat-safe bowl. Whisk until smooth.
- Pour the ganache over the custard layer and spread evenly with an offset spatula.
- Chill the assembled brownies for 2–4 hours, or until fully set.
To Serve
- Slice with a sharp knife and serve chilled. Store leftovers in the fridge for up to 5 days.
If you’re looking for a unique brownie recipe, you’ve found it in this one! The vanilla custard is honestly my favorite addition to these brownies! Let me know what you think if you make them!