Beat butter, sugar and vanilla sugar until frothy, add eggs and amarula liqueur and stir in again for at least 5 minutes. Mix the flour and baking powder and gradually fold in. Hook the chocolate and fold in as well. Place half of the batter in a separate bowl and mix with sieved cocoa powder if desired. It is also delicious if you add 50 g of coarse coconut flakes to the light-colored dough, which gives it a special taste. Grease an imperial baking tin (approx. 30cm) or springform pan and sprinkle with coconut flakes (it comes off the mold more easily) and bake in the oven preheated to 180 ° C on the middle rack for about 1 hour (knitting needle test) If you like, you can cover the cooled cake with dark chocolate or sprinkle with powdered sugar.