Beat the egg whites with a little sugar until very stiff. Beat egg yolks, sugar and vanilla sugar until frothy. Stir in eggnog and oil. Mix the flour and baking powder, sift into the egg mixture and stir in. Carefully fold in the egg whites.
Pour half of the batter into a baking pan. Stir 1 1/2 tablespoon cocoa into the rest of the batter. Fold in the mocca beans. Put the dough on the light mass and fold in a spiral.
Bake the cake in the preheated oven for about 1 hour. Please check more often after 50 minutes.
Let the cake get cold and turn it out. Sprinkle with powdered sugar and the rest of the cocoa.