Beat eggs, sugar and vanilla sugar until creamy. Add liqueur and oil and stir in. Mix flour and baking powder and also stir in. (The dough is quite thin in consistency).
Pour half the dough into a greased, flour-spread ring cake or cupcake tin (22 cm Ø; 2.5 l capacity). Sift 1 1/2 tbsp. cocoa onto the remaining dough and stir in. Fold in the mocha beans and pour onto the light-coloured dough. Use a fork to spiral the dark dough into the light dough
Bake the cake in a preheated oven (electric cooker: 175 °C / fan oven: 150 °C / gas: level 2) for about 1 hour. First let it cool down a little in the tin. Then turn it over, turn it over again and let it cool down completely. Dust with icing sugar and remaining cocoa