Separate 1 egg for the pluck cake. Knead butter, flour, 75 g sugar, vanilla sugar, cocoa, 1 egg yolk and 3 tablespoons water until smooth. Chill the dough for about 30 minutes.
Then roll out the dough (except for 50 g) between 2 layers of cling film. Line the bottom of the springform pan with baking paper. Place the dough in the pan, pull up the edge and press down.
Prick the dough several times with a fork and chill again. Beat 4 eggs and 200 g sugar until creamy. Mix curd and cream cheese, then stir in the custard powder.
Fold in the sugar-egg mixture. Pour the cheese cream into the springform pan. Roll out the remaining dough about 3 mm thin, pluck into patches and spread on the cake. Bake in preheated oven at 150 °C convection oven for approx. 1 hour.