Ingredients
1/2 cup roasted hazelnuts (crushed, or almond slices, for garnish)
1 cup heavy cream (240 mL)
8 ounces semi-sweet chocolate (228 g, finely chopped)
2 tablespoons butter (28 g, melted, for cake)
1 cup all-purpose flour (136 g, for cake)
1 cup sugar (201 g, for cake)
6 large eggs (342 g, for cake)
1 teaspoon bourbon (or rum, optional)
2 tablespoons butter (28 g, for pastry cream)
1 Pinch salt
2 tablespoons cornstarch (15 g)
3 tablespoons all-purpose flour (27 g, for pastry cream)
5 large egg yolks (90 g, for pastry cream)
1/2 teaspoon vanilla paste (or 1 teaspoon vanilla extract)
1/2 cup sugar (100 g, for pastry cream)
2 1/2 cups milk (591 mL)
Step by step
SPECIAL EQUIPMENT: KitchenAid® Artisan Stand Mixer with whisk attachment; 9-inch cake pan; pastry spatula
Make the pastry cream. Pour the milk and a quarter cup of the sugar into a saucepot and turn the heat to medium. Whisk gently to combine, and then add in the vanilla paste. Whisk again. Allow the mixture to cook without stirring until the milk is steaming and a skin begins to form on the top. Do not boil the milk.
In a separate bowl whisk together the egg yolks and remaining quarter cup of sugar. The yolk mixture is ready when it is slightly thickened and forms ribbons (about 60 seconds). Sift the flour, cornstarch and salt into the yolk mixture, and whisk again until smooth.
When milk is ready, add 1/3 of the hot milk into the yolk mixture, whisking constantly. Then, pour the tempered yolks into the saucepan with the remaining milk, stirring constantly. Increase the heat to medium high and bring to a boil while whisking. Once it starts to bubble, reduce heat to a simmer and continue to simmer the pastry cream for at least a minute. Turn off the heat, add the butter and the bourbon and use a pastry spatula to fold them into the pastry cream. Pour the cream into a glass bowl. Butter a circle in the center of a square of plastic wrap and place the buttered circle directly onto the surface of the hot pastry cream. (This will prevent skin from forming on the surface.) Refrigerate the pastry cream until cooled completely - at least three hours, but ideally overnight.
Make the cake. Preheat the oven to 350°F/177°C . Prepare a cake pan by spraying it generously with spray oil and flouring it. Be sure all surfaces are coated in flour and then shake out excess. Set aside.
Add the eggs and sugar into the KitchenAid® Artisan Stand Mixer and attach the whisk attachment. Turn to speed 6, and whisk ingredients for 4-5 minutes, or until the mixture is thick and has doubled in size. Reduce speed to stir and sprinkle ¼ cup of flour at a time into the mixture. Turn off speed after the last of the flour is added, and use a pastry spatula to fold in any remaining flour bits.
Pour the batter into the prepared cake pan and bake for 35-40 minutes, or until the cake is deep golden brown and a toothpick comes out clean. Let rest in the pan for 10 minutes, run a sharp knife along the sides of the pan to release the cake, then turn out onto a cooling rack to cool completely.
When pastry cream is fully chilled and cake is completely cooled, you’re ready to assemble the cake.
Make the ganache. Place finely chopped chocolate in a medium glass bowl. Heat the cream in a small saucepan over medium heat until it begins to gently simmer, but not boil. Pour hot cream over the chocolate and let it sit for 2-3 minutes. Then, use a pastry spatula to slowly stir the mixture and all chocolate is melted. Allow to cool for about 10 minutes so that chocolate is thick and smooth, but not watery.
Slice the sponge cake in half. With the bottom layer on your cake plate, smooth a thick layer of pastry cream to the edges of the cake. Place the cut side of the top half of the cake directly onto the pastry cream, and gently press the two layers together. Use a pastry spatula to smear pastry cream around the outside edges of the cake (but not on the top), and use your hand to press crushed hazelnuts along the side of the cake. Finally, pour a bit of chocolate ganache into the center of the top of the cake, and gently smooth the chocolate to the edges. Allow to set for a minute or two, and add additional ganache on top to create a thick layer of chocolate.
Chill the assembled cake until ready to serve.