Mix the flour, baking powder, and baking soda and sift into a mixing bowl. Add the sugar, vanilla sugar, eggs, margarine and cream. Mix everything with the hand mixer for 2-3 minutes on the highest setting to a smooth dough.
Put one half in a greased tin sprinkled with breadcrumbs, stir in the milk and cocoa under the other half and pour on the light dough. Use a fork to run through the dough in a spiral. Bake at 180 degrees, top and bottom heat for 1 hour.
Let the cake rest in the mold for 10 minutes, then let cool on a wire rack.
Sprinkle with powdered sugar or cover with chocolate icing to taste.