Carefully butter and flour a cake tin. Beat fat and Sugar until light and fluffy. Add eggs one at a time, beating thoroughly after each one. Add the baking powder and vanilla Sugar to the flour and stir in slowly. Put one-third of the mixture in another bowl and add 2-3 tblsp of sifted cocoa and 3 tblsp of milk. Put the mixture into the prepared cake in tin in layers, beginning and ending with the plain mixture. Bake at 175 °C for 50–60 minutes or until a skewer inserted in the centre comes out clean.