In a bowl mix the butter, sugar and flour.
Pour half of the mixture in another bowl.
In one bowl add the vanilla sugar and make a big dough ball.
In the other bowl mix in the cacao powder and make a big dough ball.
Place the bowls in the fridge for 45 minutes.
Preheat the oven at 200 degrees.
Place a banking paper on a baking sheet.
Take out the doughs from the fridge.
Divide each dough in 4. Make rolls.
Place 1 white and 1 black roll together and press slightly. Cut in thin slices and place each cookie on the baking paper.
Continue with the rest of the dough.
Place in the oven for 10 minutes.
Take out and let cool down.