Cream fat, sugar and vanilla sugar with the whisk of the hand mixer. Stir in the eggs one by one. Mix flour and baking powder and stir in alternately with the milk. Grease 4 preserving jars and sprinkle with sugar.
Fill half of the dough into the glasses. Stir cocoa into the other half and fill it onto the light-coloured dough. Pull spirally through the dough with a fork. Close the glasses and bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 45 minutes.
Take the cake out of the oven and remove the lid if it is not to be stored for a longer period of time. After about 10 minutes, turn the cake over and let it cool on a cake rack. Decorate the cold cakes with the grated chocolate.
Whipped cream tastes good with it.