Chop the chilled butter with the flour, add the powdered sugar and vanilla sugar, egg yolks, and a pinch of salt knead the dough and put in the fridge for 30 minutes. Then roll the dough. Put into the cupcakes forms. Inside put the plum jam and cover it with a dough. Put into the oven. Bake in 180 Celsius degrees.You can decorate tchem with Polish flag or coat of arms of your village.