Cream icing sugar and butter with the whisk of the hand mixer. Add milk, egg, vanilla sugar and salt bit by bit and stir. Stir in flour briefly. Pour the dough into a piping bag with a large star-shaped spout.
Spray fir trees on 2-3 baking trays lined with baking paper. Sprinkle with sugar pearls. Bake the trays one after the other in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-12 minutes.
Remove and let it cool down.