Bring the milk, except for 5 tablespoons, to the boil in a pot. Mix the remaining milk, pudding powder and 75 g sugar. Stir into the milk and bring to the boil again. Pour into a bowl and cover with cling film to prevent skin formation.
Let the pudding cool down. For the batter, whisk 250 g soft butter, remaining sugar, vanillin sugar and 1 pinch of salt with the whisks of the hand mixer until creamy. Gradually stir in the eggs.
Mix flour, cornstarch and baking powder and stir in by the spoonful. Grease a springform pan (26 cm Ø) and spread approx. 3 tablespoons of dough evenly over it. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for 8-10 minutes until golden brown.
Remove from the springform pan base immediately after baking and allow to cool. In this way, bake 7 thin bases one after the other. For the cream, whisk the remaining butter for 10-15 minutes until creamy white.
Stir in chocolate pudding by the spoonful. Finally, stir 1 tablespoon of cocoa into the finished chocolate butter cream. Remove 6-7 tablespoons of cream and fill into a piping bag with star-shaped spout.
Spread the rest of the cream thinly on the sponge cake bases and put them together to form a cake. Do not spread the top cake base. Put the cake in a cool place. Meanwhile melt the chocolate coating in a hot water bath and let it cool down.
Then reheat again. Pour the chocolate coating over the cake and allow to set. Spray a buttercream wreath on the edge of the cake and sprinkle with pistachios. Keep cool until serving.
Results in about 16 pieces.