Preheat the oven to 175 °C convection oven.
For the sponge cake base, beat the eggs and sugar with a mixer until creamy. Mix flour, baking powder and cocoa powder and fold in.
Spread the bottom of a cake springform pan (28 cm ø) with parchment paper, pour in the batter.
Bake the sponge for about 20 minutes. Let the base cool on a cake rack, then cut it once horizontally. The top layer should be thinner than the bottom.
For the filling, whip the cream until almost stiff, then stir in the sugar. When the whipped cream is completely stiff, whisk in the custard powder and the amaretto.
Place the bottom sponge cake layer on a serving plate and enclose with a flexible springform pan. Pour in the chocolate cream and cover with the top cake layer.
Whip the whipped cream until stiff for the decoration. Fill about 1/3 of it into a piping bag. Spread the rest over the top of the cake. Then, using the piping bag, place thick dabs of cream on top of the rim. Draw lines of chocolate sauce in the center of the cake.
Top the dots of cream with the chocolate flakes.