Boston Cream Cake

Some cakes just hit differently—this one always has. I still remember the first time I made a Boston Cream Cake from scratch.

I didn’t overthink it, didn’t try to make it fancy. Just two layers of soft, golden sponge, a thick layer of vanilla custard in the middle, and a glossy, no-nonsense chocolate topping that looked too pretty to mess with.

But I did mess with it—I took a knife and cut myself a slice, and I knew it was the only kind of mess I’d happily make again and again.

This cake doesn’t rely on trends or decorations. It’s not trying to be anything but what it is: rich, soft, creamy, and full of old-school goodness.

It feels like something homemade in the best way—not perfect, but personal. The kind of cake you make when you want to treat someone, even if that someone is just you.

So if you’ve never tried baking it yourself, don’t worry. I’m walking you through the whole thing—no fluff, no complicated instructions.

Just real, doable steps that lead to the same slice I had sitting on my plate that day, ganache dripping slightly down the side, and custard holding its own in the middle like a little secret worth keeping.

Boston Cream Cake Recipe

Ingredients

For the Sponge Cake:

1 ½ cups (180g) all-purpose flour (sifted)
1 ½ tsp baking powder
¼ tsp salt
½ cup (115g) unsalted butter, softened
1 cup (200g) granulated sugar
3 large eggs, room temperature
1 tsp pure vanilla extract
½ cup (120ml) whole milk, room temperature
¼ cup (60ml) hot water

For the Pastry Cream Filling:

2 cups (480ml) whole milk
½ cup (100g) granulated sugar
¼ tsp salt
4 large egg yolks
¼ cup (30g) cornstarch
3 tbsp (40g) unsalted butter
1 tsp pure vanilla extract

For the Chocolate Ganache Topping:

¾ cup (180ml) heavy cream
150g (about 1 cup) dark or semi-sweet chocolate (chopped into small pieces)
1 tsp unsalted butter (for shine)

Instructions

Step 1: Make the Sponge Cake

Preheat your oven to 350°F (175°C). Grease and line two 8-inch round cake pans with parchment paper.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large mixing bowl, cream the softened butter and sugar together until pale and fluffy (3–4 minutes using a hand mixer on medium-high).
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Reduce speed to low. Add the flour mixture in two additions, alternating with the milk. Mix just until combined—do not overmix.
Stir in the hot water at the end to loosen the batter slightly. The batter will be smooth and pourable.
Divide evenly between the prepared pans and bake for 22–25 minutes or until a toothpick inserted in the center comes out clean.
Let cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Step 2: Make the Pastry Cream

In a medium saucepan, heat the milk over medium heat until steaming (do not boil).
In a separate bowl, whisk together egg yolks, sugar, salt, and cornstarch until smooth and slightly pale.
While whisking, slowly pour about ½ cup of the hot milk into the egg mixture to temper it.
Gradually pour the tempered egg mixture back into the saucepan of remaining milk, whisking constantly.
Cook over medium heat, stirring continuously, until the mixture thickens into a custard (this happens fast once it starts).
Remove from heat. Stir in butter and vanilla extract until smooth.
Pour into a shallow dish, press plastic wrap directly onto the surface to prevent a skin from forming, and chill for at least 1–2 hours until set.

Step 3: Make the Ganache

Place chopped chocolate and butter in a heatproof bowl.
Heat the cream in a small saucepan over medium heat just until it begins to simmer (don’t boil).
Pour the hot cream over the chocolate. Let it sit undisturbed for 2 minutes, then stir until glossy and smooth.
Let it cool slightly until it thickens to a pourable glaze consistency (not too runny).

Step 4: Assemble the Cake

Place one cake layer on your serving plate.
Whisk the chilled pastry cream briefly until smooth, then spread it evenly over the bottom cake layer—stay within ½ inch of the edge to prevent overflow.
Gently place the second cake layer on top and press lightly to secure.
Pour the chocolate ganache over the top layer, allowing it to naturally drip down the sides.
Chill the assembled cake for 1–2 hours to set the ganache and firm the cream layer before slicing.

Final Notes

For the cleanest slice, use a sharp knife dipped in warm water and wiped dry.
Store the cake in the fridge and consume within 2–3 days for best texture and flavor.

How Do I Keep The Custard From Leaking Out Of My Boston Cream Cake?

The custard slipping out can ruin both the look and feel of your cake — but a few small tricks make a big difference:

Cool everything completely: The custard and cake layers must be fully cooled before assembling, or the filling will slide right out.
Don’t overfill: Use just enough custard to cover the layer — about ¾ inch thick is plenty.
Pipe a frosting “dam”: If you want extra security, pipe a ring of whipped cream or thick buttercream around the edge before spreading the custard inside.
Use a serrated knife to level the layers: Uneven layers can cause the top to tilt and squeeze the filling out.
Chill after assembling: Once the cake is stacked, refrigerate it for at least 1 hour before topping with ganache or slicing. This helps the filling firm up.

Why Is My Sponge Cake Dry Or Dense?

A light sponge is key for Boston Cream Cake — and a few simple mistakes can make it heavy or dry:

Too much flour: Always spoon flour into the cup and level it with a knife — don’t scoop directly from the bag.
Overmixing the batter: After adding the flour, mix just until the ingredients come together. Overmixing knocks out the air.
Not using room temperature eggs or milk: Cold ingredients won’t blend properly and can make the cake tough.
Overbaking: Start checking your cake a few minutes before the timer goes off. The cake should spring back when gently touched.
Wrong pan size: If your pan is too small, the batter bakes unevenly and dries out at the edges.

Can I Make Boston Cream Cake Ahead Of Time?

Yes — in fact, this cake tastes even better the next day after it’s had time to chill and set. Here’s how to plan it:

Bake the cake layers a day in advance: Wrap them tightly and keep them at room temperature.
Make the custard up to 2 days ahead: Store it in the fridge with plastic wrap touching the surface.
Assemble the cake the night before: It helps everything hold together and gives the custard time to set nicely.
Add ganache on the same day you serve: It looks glossier and fresher that way.

Can I Use a Boxed Cake Mix For Boston Cream Cake?

Yes, you can! It’s a quick shortcut when you don’t feel like baking from scratch. Choose a soft yellow or butter cake flavor for best results.

Use milk instead of water: It adds more richness.
Add an extra egg: This makes the texture softer and more like a bakery cake.
Swap oil for melted butter: It gives better flavor and structure.

How Do I Make The Custard Filling Thicker?

A thick, sturdy custard holds up better between the layers — here’s how to make sure yours doesn’t run:

Add more cornstarch: Use 1 extra tablespoon if your recipe feels too soft.
Cook it a little longer: Keep whisking over medium heat until large bubbles form and the custard is visibly thick.
Use only yolks, not whole eggs: Yolks thicken custard better and give it a richer texture.
Let it cool before using: Warm custard will spread too much. Chill it until it holds its shape on a spoon.

Can I Make This Cake Without Eggs?

Yes — and it can still taste amazing with the right swaps. Use one of these replacements for each egg in your recipe:

1 tbsp cornstarch + 2 tbsp water
¼ cup plain yogurt
¼ cup mashed bananas (for a slightly fruity flavor)
¼ cup unsweetened applesauce

Is It Okay To Freeze Boston Cream Cake?

Freezing is possible, but some parts freeze better than others. Here’s what you should know:

Freeze only the cake layers: Wrap them tightly in plastic and foil and freeze for up to 2 months.
Avoid freezing the custard: It changes texture and becomes watery after thawing.
Ganache freezes well: You can make it ahead, freeze it in a container, and gently reheat before using.