Put the first 8 ingredients in a mixing bowl and work into a smooth dough in about 2 minutes. Pour half of the batter into a cup cake pan. Mix the remaining dough with the milk and cocoa and pour onto the light dough. Pull through the dough in a spiral with a fork.
The oven does not need to be preheated. Bake the cake with hot air 160 °, top / bottom heat 180 °, gas level 2-3 for about 60 minutes.