Knead the butter in pieces, sugar, flour, vanillin sugar and egg first with the dough hooks of the hand mixer, then with your hands to a smooth dough. Wrap dough in foil and chill for about 30 minutes. Roll out to a thickness of approx. 3 mm on a work surface dusted with flour. Cut out pockets and shoes. Put cookies on 2-3 baking trays lined with baking paper. Bake one after the other in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 8-10 minutes. Let them cool down.
Stir icing sugar and egg white until smooth. If the icing is too firm, stir in some water. Put 2 tablespoons of icing aside. Cut the rest of the icing in half and colour it mint and pink. Pour the icing into 3 piping bags. Paint biscuits with it and decorate with sugar pearls. Leave to dry