Mix flour, sugar with salt and lemon zest. Add the cold butter in pieces. Now chop all ingredients with a large kitchen knife until the amount is fine crumbs. Add the egg and egg yolks and quickly combine everything together with your hands to make a smooth dough. Wrap in plastic wrap and refrigerate for 3 to 4 hours. Roll out the dough onto a floured surface to a thickness of 5 mm. Cut out any shapes, And place on a baking sheet lined with parchment paper.
Stir the egg yolk with the milk and spread on the cookies.
Bake in the oven at 200 degrees for about 10 minutes.