Preheat the oven at 175 degrees Celsius
Mix the margarine, sugar and vanilla sugar with an electrical mixer.
Add the potato flour and the egg, and continue to mix everything to a sticky dough.
Place a baking paper on a baking sheet.
Make small round cookies on the paper. Make sure they are not too close to each other, because they will grow in shape in the oven.
Place the cookies in the middle of the oven for ten minutes. If you prefer the cookies very dry increase the time in the oven with five more minutes.