Cream butter, icing sugar and vanilla sugar with the whisks of the mixer. Stir in orange zest, eggs and milk one after the other. Mix flour and cocoa. Stir in briefly.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Line two baking trays with baking paper. Pour the dough into a piping bag with a large star-shaped spout. Spray a total of approx. 80 flat tuffs (approx. 2 cm Ø each) onto the baking trays, pulling the spout slightly to the side.
Bake in a hot oven for 6-8 minutes one after the other. Remove from the oven and leave to cool for about 5 minutes. Then remove from the baking tray together with the paper and let it cool down.
Pour the chocolate cream into a freezer bag. Cut off one corner. Spray the underside of 40 biscuits with the chocolate cream. Put the remaining biscuits on top and press them on a little. Cool for about 30 minutes.