Combine flour, butter, sugar, egg, baking powder and vanilla sugar in the bowl of a food processor; process until the mixture comes together to form a dough. Chill the cookie dough in the fridge for 1 hour.
Preheat oven to 180 C / Gas 4. Lightly grease a baking tray.
Roll out the dough to about 1/2cm thick and cut out stars of two different sizes. Place on the baking tray.
Bake in preheated oven for 8 to 12 minutes. Allow to cool slightly and spread the back of the smaller stars with jam. Press onto the larger stars and let cool completely. If you like, dust with icing sugar.