Place flour on work surface or in a large bowl.
Add sugar, vanilla sugar and salt. Cut the cold butter into small pieces and spread the flakes around the flour.
Make a well in the flour and add the yolk or egg. Quickly knead all the ingredients into a dough with cold hands. You can also wear gloves for kneading.
Shape the dough into a brick and wrap in plastic wrap. Let it rest in the refrigerator for 1-2 hours before further processing.
Then continue to process the shortbread dough as desired.
Preparation Tip:
Flavor the shortbread with some finely grated orange or lemon zest (untreated) and add finely chopped walnuts or peanuts to the batter.