Mix butter, vanilla sugar, lemon zest and icing sugar with the whisk of the hand mixer until creamy. First stir in eggs, then flour. Pour the dough into a piping bag with a medium star-shaped spout and squirt onto 2 baking trays lined with baking paper in an S-shape (approx. 8 cm long). Bake the trays one after the other in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 8-10 minutes
Remove the cookies and let them cool on a cake rack for about 20 minutes. Coarsely chop the chocolate coating, melt it over a warm water bath and let it cool down for about 10 minutes. Dip half of each cookie in chocolate coating and place on baking paper. Leave to dry for approx. 30 minutes.
Waiting time approx. 1 hour