Separate eggs. Beat egg whites and 5 tablespoons of water until stiff. Add sugar and vanilla sugar while stirring. Beat the egg yolks into the mixture bit by bit. Mix flour, cornstarch, baking powder and cocoa.
Sieve onto the egg foam mixture. Add the chocolate and fold in loosely. Line the bottom of a springform pan (26 cm Ø) with baking paper, fill in the dough and smooth it down. In the oven
Let it cool down. Cut the biscuit twice. Soak gelatine in cold water for about 5 minutes, squeeze out, dissolve and mix with advocaat. Put it in a cold place. Whip cream, vanillin sugar and sugar until stiff.
When the egg liqueur begins to gel, stir in the cream in portions. If necessary, refrigerate again briefly. Fill the cake with almost half of the advocaat cream. Spread some of the remaining cream all around the cake.
Put the rest of the cream in a piping bag with a star or rose spout and refrigerate again. In the meantime, sprinkle the edge and centre of the cake with chopped pistachios. Spray the cream edge and put the cake in a cool place for about 2 hours.
Decorate with sugar flowers and eggs and lemon balm just before serving. Results in about 16 pieces.