Beat the eggs, sugar and vanillin sugar until fluffy. Add egg liqueur and oil and stir in. Mix flour and baking powder, sieve onto the egg oil mass and mix. Fill half of the dough into a greased, flour-spread pancake tin (2.5 litres capacity).
Sift 1 1/2 tablespoon of cocoa onto the remaining dough and stir in. Fold in the mocha beans and pour the dough onto the light-coloured mixture. Use a fork to spiral the dark dough into the light dough.
Bake the cake in a preheated oven (electric: 175 °C/ gas: level 2) for about 1 hour. Then let it cool down a little, turn out of the tin and let it cool down completely. Dust with icing sugar and remaining cocoa.
Results in about 20 pieces.