Bake the Sponge Cake

Preheat the oven to 350°F (180°C) and butter and line with parchment two 8-inch (20cm) round cake pans. Set aside.

In a large bowl, whisk together the flour, baking powder and salt. Set aside.

In a stand mixer bowl with a whisk attachment, add the egg yolks, 1 cup (8 oz/225 g) of sugar and vanilla and beat on high speed for about 5 minutes, until pale and thick.

Add this egg mixture to the dry ingredients and fold in briefly followed by the milk and melted butter. Set aside.

Wash the bowl and whisk.

Again in the stand mixer, whip the egg whites on medium-high speed to soft peaks, about 3 minutes. While the mixer is still running, gradually add in ¼ cup (2 oz/57 g) of granulated sugar and continue beating to stiff, glossy peaks, about 3 more minutes.

Using a large metal spoon, gently fold the egg whites into the yolk mixture until just combined.

Divide the batter evenly between the prepared cake pans and bake for 25-28 minutes, until a cake tester inserted in the middle comes out clean.

Let the cakes cool in the pans for 10 minutes and then invert them onto a wire rack to cool completely.

Make the Coffee Syrup

Combine the coffee and brandy in a bowl set aside until assembly.

Make the Mascarpone Buttercream

In the bowl of a stand mixer fitted with a whisk attachment, whip the butter and mascarpone on high until combined. Take care not to over mix or the mascarpone will separate.

Turn the mixer to low and gradually add the powdered sugar, stopping every now and then to scrape the sides of the bowl. Once all of the sugar is incorporated, turn the speed up to high again and whip the butter and sugar together for a few minutes, until fluffy.

Lower the speed to low again and whisk in the cream, vanilla extract, and salt.

Decorate the Cake

Once the cake layers are cool, first cut the domes off of both layers if any, then split the layers in half to create 4 layers.

Carefully place the first cake layer on a serving plate and brush with a ⅓ of the coffee mixture all over the surface allowing it to soak in. Next spread about ¾ cup of frosting evenly over the layer, all the way to the edges. Continue to add a layer, brush with coffee and spread frosting.

Cover the top and sides of the cake with a smooth layer of frosting, then place the remaining frosting in a large piping bag fitted with a large star tip.

Pipe rosettes all over the top of the cake, starting with the outside edge and working your way into the center. If not serving right away, refrigerate for up to one day. Cover loosely with plastic wrap only after the frosting is cold and hard, after a few hours.

Serve the Cake

Just before serving, dust the rosettes with cocoa powder. Serve the cake at room temperature. Keep remaining in the fridge for up to 3 days.