Separate eggs and beat until stiff. Mix egg yolks with sugar and vanilla sugar well (until the dough “waves”). Then add oil and water and mix briefly. Mix flour with baking powder and fold in alternately with snow. Pour 2/3 of the mixture into the buttered and floured cake pan. Add cocoa to the remaining third, as much as you like, and let it flow into the mold, creating a chocolate ring. Then place in an oven preheated to 160° (convection oven). Bake for about 30 minutes.