Cream butter, icing sugar and vanillin sugar with the whisk of the hand mixer. Stir in the egg. Mix cocoa and flour and knead in.
On a work surface sprinkled with flour, work into a smooth dough with your hands. Wrap dough in foil and chill for about 1 hour. Roll out the dough 3-4 mm thin on a floured work surface and cut out approx. 55 boots (approx. 6 cm high).
Knead the remaining dough and roll it out again.
Place the biscuits on 2 baking trays lined with baking paper. Bake one after the other in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 8 minutes. Remove the biscuits from the oven and let them cool down on a cake rack.
Roughly chop the chocolate coating. Melt the couverture and coconut oil in a bowl over a warm water bath. Brush the biscuit surface with couverture using a brush and decorate with sugar pearls.
Put the biscuits in a cool place for about 1 hour until the chocolate is firm.