Cut the butter into small pieces. Add the flour, powdered sugar, vanilla sugar and egg and knead everything. Cover the dough in the refrigerator for about an hour.
Roll out the dough on a 40 x 30 cm baking sheet lined with baking paper and bake at 175 degrees for about 25 minutes.
When the dough has cooled down a bit, quarter it lengthways to make 4 rectangles.
Make a frosting from water and powdered sugar.
Now spread the jam on two of the plates, and spread the icing on the other two. Then you put a plate with the topping on top of a plate with jam. Now you cut each plate into 5 sections so that you end up with ten cuts.
If you want, you can sprinkle the slices with colored sugar pearls.