For the sponge cake, separate the eggs and beat the egg whites with salt in a food processor until stiff peaks form. Gradually add the sugar, a little at a time, and continue beating until the mixture is glossy and peaks form. Now beat in the egg yolks one at a time, continuing to beat. Combine the flour, cornstarch, custard powder, and baking powder, then sift and carefully fold into the egg foam mixture using a whisk. Bake the sponge cake in a 26 cm cake ring on a rack lined with baking paper in a preheated oven at 190°C for about 30 minutes using top and bottom heat. Allow to cool; ideally, bake the day before.

To make the drink, bring the milk to a boil with the sugar and cocoa powder, then add the cold espresso and amaretto and set aside.

For the cream, combine the mascarpone, quark, sugar, and vanilla sugar until creamy and the sugar has completely dissolved. Whip the cream with Sahnestabil until stiff peaks form and fold into the quark mixture. Stir in the amaretto and egg liqueur, reserving some for decoration. Then fold in the grated chocolate.

Cut the sponge cake crosswise into three equal pieces and place a flexible cake ring around the bottom layer. Drizzle one-third of the filling onto the first layer, spread just under half of the cream on top, place the second layer on top, and repeat. Place the third layer on top of the last layer of cream and also fill it with the filling. Spread with some of the remaining cream and refrigerate for at least 3 hours.

Carefully remove the cake ring, spread the edge of the cake with cream, and sprinkle with grated chocolate. Dust the top of the cake thickly with cocoa powder.

For the decoration, fill the remaining cream mixture (without grated chocolate) into a piping bag with a star nozzle and pipe 16 identical rosettes on top and decorate with chocolate zebra rolls as desired.