Butter must be stirred and beaten until it is foamy. Slowly add sugar, vanilla sugar, eggs, salt and rum flavour. Mix flour and baking soda together. Take turns adding the flour and the milk. Only add enough milk to make the dough heavy, so it looks as if it is tearing off the spoon. Put 2/3 of the dough into a greased, ring shaped cake tin which has been sprinkled with breadcrumbs.

Add the cocoa, the 25g sugar and the remaining milk to the rest of the dough until it reaches the same consistency as the first half. Spread the darker dough onto the lighter one. In order to achieve a marble pattern, draw a fork through the two layers as if you were forming a spiral. Bake in a pre-heated 190*C oven for 50 - 65 minutes or until cooked (wooden skewer when inserted comes out clean).