Beat the eggs with the sugar and salt until the mixture triples in volume and turns pale and thick. Gently fold in the sifted flour and cocoa using a spatula. Divide the batter between 3 lined round cake pans (or bake them one after another) and bake at 350°F (180°C) for about 10–12 minutes. Let the sponge layers cool completely.

Beat the mascarpone with the powdered sugar until smooth and creamy. Add the cold heavy cream and whip until the mixture becomes thick and holds soft peaks. Finally, mix in the concentrated instant coffee. Divide the cream in two portions for filling the layers and transfer the remaining part to a piping bag for decorating the top.

Place the first sponge layer on a serving plate. Using a piping bag fitted with a round tip, pipe a ring of cream “bubbles” around the outer edge, then fill the center with more cream and gently smooth it with a spatula. Set the second sponge layer on top of the cream. Press lightly, then repeat the process: pipe cream “bubbles” all around the edge of the layer and fill the middle with cream.

Place the final sponge layer on top. Melt the chocolate together with the cream over low heat or in the microwave and stir until smooth and glossy. Let it cool slightly, then spread it evenly over the top sponge layer.

To finish, decorate the top of the cake with another ring of cream “bubbles” around the edges, just like on the previous layers.