Knead the flour, butter in pieces, sugar, vanilla sugar, egg, salt and poppy seeds with the dough hooks of the hand mixer to a smooth dough. Wrap in foil and chill for about 30 minutes
Roll out the dough in portions on a floured work surface to a thickness of 2-3 mm. Cut out approx. 45 stars each in 2 different sizes (5.5 + 7 cm Ø). Spread on 3-4 baking trays lined with baking paper. Cut another hole (2.5 cm Ø) in the middle of the smaller stars. Bake one after the other in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 8-12 minutes depending on the size of the stars. Let the biscuits cool down on cake racks
Stir plum puree until smooth. Put a blob of plum puree in the middle of each of the larger stars, place the smaller stars offset on top and press down slightly. Dust with icing sugar
Waiting time approx. 1 hour