Roughly chop the chocolate. Cream butter, sugar, rum, orange peel, salt and vanilla sugar with the whisk of the hand mixer until the sugar is dissolved. Stir in the egg. Mix flour and baking powder and stir in. Using a tablespoon, place 9 piles of dough on 3 baking trays lined with baking paper and press flat. Bake the trays one after the other in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-12 minutes. Remove from the baking tray, place on a grid and allow to cool