Flower Cookies with Icing
Combine flour, butter, powdered sugar, egg yolks and vanilla sugar, then with your hands knead into a smooth dough. Wrap in foil and chill for 30 minutes.
Roll out the dough on a lightly floured surface until about 3-4 mm thin (approximately 1/8 inch), cut out cookies in flower shapes and place on a parchment paper-lined baking sheet, leaving some distance between each cookie, and bake on the center rack of a preheated oven at 200°C (approximately 400°F) for about 10 minutes. Remove and let cool.
Stir the powdered sugar with a little water until a thick icing forms. Divide into portions and dye with the food coloring, if desired. Brush the cookies with the glaze and let dry.