Cream 250 g fat, 225 g sugar and vanillin sugar. Add eggs bit by bit and stir until creamy. Mix flour and baking powder, sieve and stir into the fat egg mass with 4 tablespoons of milk.
Spread half of the dough on a greased baking tray. Stir the remaining milk and cocoa into the remaining dough. Spread the dark dough on the light one. Pull the dough spirally with a fork.
Smooth the dough. Bake in the preheated oven (electric: 175°C/ gas: level 2) for 20-25 minutes. Let the cake cool down. Sort the berries. Boil up peach and lemon juice, remaining fat and sugar.
Stir cornflour and some water until smooth, stir into the boiling liquid and bring to the boil again briefly. Stir in egg yolk. Carefully fold in 2/3 of the blackberries and spread Berry Curd on the marble dough.
Sprinkle the rest of the blackberries and raspberries on the cake and let it set. Serve the cake decorated with lemon slices. Makes about 24 pieces.