Knead the soft butter and nougat mixture together. Add egg, vanilla sugar and salt and mix well. Mix flour and baking powder and gradually sift into the nougat mass. Knead well with the dough hooks of the hand mixer. Form the dough into a ball and put it in a cool place wrapped in aluminium foil for about 1 hour. Roll out the dough on a floured work surface to a thickness of about 1/2 cm. Cut out stars and hearts and place them on a baking tray lined with baking paper.
Bake in a preheated oven (electric: 175 °C/ gas: level 2) for about 12 minutes. Let cool off well. Mix the icing sugar with the lemon juice to a thick paste. Take off about 2 tablespoons and mix with the cocoa. Spread each biscuit with white icing sugar. Place a drop of cocoa icing in the moist, light icing and pull it apart with a pointed piece of wood (e.g. toothpick)
Preparation time approx. 1 1/4 hours