Beat soft butter with powdered sugar and vanilla sugar until splendid. Then add starch and half a glass of flour, whisk again with a mixer. Add the rest of the flour and knead with a spoon until smooth. Refrigerate for 1 hour.
Paste the pastry onto a covered parchment using a pastry bag or a regular spoon.
Bake at 180 degrees for 20 minutes. Let cool and serve.