Roll out the puff pastry and cut into squares.
Take a square of dough and fold into a triangle.
Now cut into the triangle on both sides without cutting the dough all the way through.
Unfold the dough triangle, then fold the cut edges over each other and press firmly.
Put a dollop of plum jam in the middle.
Place the puff pastries on a baking sheet lined with baking paper, brush with egg yolk and sprinkle with vanilla sugar.
Bake 15 - 20 minutes in a preheated oven at 180 °.
Remove and sprinkle with powdered sugar.