Cream butter in pieces, icing sugar, vanillin sugar and salt with the whisk of the hand mixer. Stir in egg and orange peel. Stir in flour and milk briefly. Pour the dough into a piping bag with a medium-sized star-shaped spout (approx. 11 mm Ø). Line 2 baking trays with baking paper. Spray ice crystals (approx. 6 cm Ø) on top, while spraying a wide tuff in the middle and around it approx. 6 smaller ones.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 8 minutes one after the other. Remove and let cool off. Chop both types of couverture separately and melt carefully over a warm water bath. Spread half of the biscuits with white couverture, the other half with darker. Sprinkle with orange peel and leave to dry
Preparation time approx. 50 minutes. waiting time approx. 1 hour