Mix the baking mix, margarine and egg yolk to a smooth dough. Form dough into 2-3 cm thick rolls, cut into 1 cm thick slices and turn into balls. Place balls on a baking tray lined with baking paper and flatten with a floured fork. Bake in a preheated oven (electric: 175 °C/ gas: level 2) for 12-15 minutes.
Melt the chocolate coating separately. Dip some cookies partially into the white chocolate coating and let them dry. Pour the rest of the couverture into two freezer bags, cut off a tiny corner of each and draw strips over the cookies. Results in about 32 pieces