Black cocoa sponge cake

1. Preheat the oven to 165°C (325°F) and line three 6-inch (15 cm) round cake pans with parchment paper.
2. In a large bowl, sift together the cake flour, black cocoa powder, baking powder, baking soda, and salt.
3. In another large bowl or the bowl of a stand mixer, whisk the eggs, granulated sugar, vegetable oil, and vanilla extract until smooth.
4. Add the buttermilk and coffee (or water) and mix until combined.
5. Gradually add the dry ingredients and mix just until a smooth, dark cake batter forms.
6. Divide the batter evenly between the prepared cake pans.
7. Bake for about 40 minutes, until a toothpick inserted in the center comes out clean or with a few moist crumbs.
8. Let the cakes cool in the pans for a few minutes, then run a knife around the edges and carefully remove them. Place the cakes upside down on a wire rack and let them cool completely.

Black Cocoa Mascarpone Filling

1. In a large bowl, whisk the mascarpone, cold heavy cream, powdered sugar, vanilla, and black cocoa powder with an electric mixer until smooth and creamy.
2. Transfer the frosting to a piping bag.

Assembly

1. Trim the tops of the cakes if needed to create even layers.
2. Place the first cake layer in a deep cake pan lined with plastic wrap or inside an adjustable cake ring.
3. Spread a layer of mascarpone filling and smooth with an offset spatula.
4. Add the second cake layer and repeat the process. Finish with the final cake layer.
5. Cover with plastic wrap and chill for 1 hour in the refrigerator or 20 minutes in the freezer.

Black Cocoa Mascarpone Frosting

1. In a large bowl, combine the mascarpone, cold heavy cream, sifted powdered sugar, and black cocoa.
2. Using an electric mixer on low to medium speed, beat for about 1 minute until thick and smooth.

Frosting and Decoration

1. Unmold the cake and place it on a cake board on a rotating cake stand.
2. Apply a thin crumb coat of mascarpone frosting with an offset spatula.
3. Add a second layer of frosting and smooth the cake with a scraper or frosting smoother.
4. Chill the cake in the freezer for 30 minutes before removing the top acrylic disc if using.

Chocolate Drip

1. Heat the chocolate, heavy cream, and black cocoa in the microwave in 20-second intervals until smooth and fluid.
2. Let the glaze cool slightly, then pour the chocolate drip over the top of the cake.
3. Decorate with the remaining mascarpone frosting using a piping bag fitted with a 1B nozzle.
4. Serve immediately or refrigerate until ready to serve.