Sift the flour onto the work surface. To press a hollow in the middle. Put the sugar, vanilla sugar and eggs in the well. Cut the butter into flakes on the edge of the flour. Knead everything from the outside to the inside with cool hands to form a smooth dough.
Wrap the dough in foil and let it rest for 1 hour in the refrigerator.
Then roll out the dough about ½ cm thick, cut out and place on baking paper and brush with egg yolk.
Bake at 200 ° C on the middle rack for 10 - 15 minutes until golden yellow.