In a bowl, combine all ingredients except the egg yolks and sugars. Rub in the butter. Then mix in the egg yolks and knead well to form a dough.
Place the dough in the fridge and chill for 2 hours. Preheat oven to 180 degrees C.
Grease a baking tray with butter. Roll out the dough into pencils about 1cm thick, then cut into 5cm portions. Form the portions into crescents and place carefully on the baking tray.
Bake 10 minutes until light brown.
Mix together the icing sugar and vanilla sugar in a large bowl and gently toss the still warm cookies in the sugar, a few at a time.