Cream 250 g butter, sugar, salt and 1 packet of vanilla sugar with the whisks of the hand mixer. Stir in the eggs one by one. Mix flour, baking powder and cocoa and stir in alternately with milk and liqueur.
Stir in 250 g chocolate crunchy pearls. Spread the dough into a greased, floured fat pan of the oven (34 x 38 cm) and bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see
manufacturer) bake for about 30 minutes. Remove and let cool on a cake rack.
Roast the hazelnut flakes in a pan without fat until golden brown, remove. Coarsely chop 100 g chocolate crunchy pearls. Coarsely chop the chocolate and melt with butter over a warm water bath. Mix sour cream and 1 packet of vanilla sugar.
Stir the chocolate and butter mixture into the sour cream.
Spread the chocolate sour cream on the cake. Spread chopped balls and hazelnut flakes on top. Chill for about 30 minutes. Cut into pieces and place on a plate.