Chocolate Boston Cream Cake

This was the cake I made for my mom's birthday. She's a chocoholic like myself so every year when I ask her what type of cake she wants for her big day the answer is always the same 'something very chocolaty'. Her favorite cake is the Sachertorte (this one) and I've been baking it for the last two years so it was about time to try a new recipe. 

As I was browsing through my cookbooks I saw a super tempting recipe of Boston Cream Doughnuts and suddenly I remembered how tasty my pastry cream is. So that recipe gave me the inspiration to bake a chocolaty version of the famous Boston Cream Pie and oh boy! it was a total success!!!

I baked two classic chocolate génoise cakes, spread a super (SUPER) generous amount of smooth pastry cream between each layer and frosted this fluffy and tender birthday cake with my go-to dark chocolate ganache. The 70% dark chocolate I use to make this ganache adds a beautiful and irresistible contrast to the sweetness of the vanilla pastry cream.

I hope you like it!

Now I'm off to enjoy this long Easter weekend we have in Spain. :-)

Receta en español aquí!

Ingredients
(Yield: one 22cm/9-inch diameter cake with two layers).

- For the chocolate génoise, make two recipes with the following ingredients:
60 g all-purpose flour.
40 g pure cocoa powder.
4 large free-range eggs, at room temperature.
Pinch of baking soda.
120 g organic cane sugar.
1 teaspoon pure vanilla extract.
50 g organic butter, melted.

- For the pastry cream filling:
5 free-range egg yolks, at room temperature.
125 g organic cane sugar.
50 g cornstarch.
625 ml milk of your choice, at room temperature.
2 teaspoons pure vanilla extract.
75-100 g white chocolate, chopped.

- For the dark chocolate ganache:
200 g dark chocolate, chopped.
250 ml milk of your choice.*
2 tablespoons organic cane sugar.
Pinch of salt.
1 1/2 teaspoons pure vanilla extract (optional).

- Decoration:
White chocolate, grated.

*Notes: 

- For the pastry cream I always use low-fat milk but you can use full-fat milk.

- For the dark chocolate ganache I like to use soy milk but you can also use almond milk.

Directions

- To make the chocolate génoise:

The quantities listed above are for one cake layer so to make a two-layer cake you will need to make two recipes.

Lightly grease with nonstick cooking spray and line the bottom with parchment paper of a round 22 cm/9-inch cake pan (or if you are going to make two layers like me, prepare two pans).

Preheat the oven to 170ºC/338ºF.

In a large mixing bowl sift together the flour, cocoa powder and baking soda. Set aside.

In a small saucepan over low heat, melt butter and set aside in a warm place.

In the bowl of your stand mixer place the eggs, sugar and vanilla extract and whisk on high speed until the mixture looks pale and fluffy, it should have tripled in volume.

Gently sift flour mixture over egg mixture in three additions using a spatula. Right before the last addition carefully fold in the still-warm butter until the mixture is just evenly combined. Take care not to overmix and deflate the batter.

Spread batter evenly in the prepared pan and lightly tap on the counter to get rid of possible air bubbles.

Bake for 20-25 minutes, or until the top springs back when touched. Let sit in pan on a wire rack for 10 minutes approximately. Remove from pan and let cool completely.

Repeat the process to make a second layer.

- To make the pastry cream:

In a medium saucepan bring the milk to a boil. Stir in the vanilla extract and set aside.

In a small mixing bowl vigorously whisk the egg yolks and sugar until pale. Gradually add in the cornstarch and keep whisking until fluffy. Add in the milk and stir until incorporated. 

Set this mixture over a medium-low heat again and cook, stirring constantly to prevent curdling, for a minute or two approximately. Once the cream starts to thicken finish the cooking process away from the heat, stirring quickly and vigorously to get a smooth, velvety pastry cream. Add in the white chocolate until fully melted and incorporated, from 75 g to 100 g, it's up to your taste.

Store the pastry cream covered with plastic wrap, touching directly the surface of the cream to prevent a skin from forming on the top.

Let it cool completely before using.

- To make the dark chocolate ganache:

Put the milk, sugar and salt in small saucepan and cook over medium heat until it begins to boil.

Remove from the heat and add in the chopped chocolate, gently whisk until the chocolate is fully melted. If using, add in the vanilla extract and stir until the ganache looks smooth and glossy. Keep the ganache at room temperature.

- To assemble the cake:

Spread a generous amount of vanilla pastry cream over the first layer and carefully place the second layer on top.

Cover the whole cake with half of the ganache, refrigerate until set and finish the coating with the remaining ganache. Store refrigerated.

Decorate with grated white chocolate and let the cake set at room temperature for about 10-15 minutes before serving.