Rub butter with powdered sugar with a spoon until smooth. This butter should be at room temperature.
Add the egg and again bring the mixture to a homogeneous state with a spoon.
Finally, add the flour and knead with your hands into a plastic dough.
Wrap the dough in cling film and refrigerate overnight.
Preheat oven into 200 °C.
Roll out the dough to a thickness of 3 mm (see the Tips section below for more details) immediately on baking paper or a baking mat. Go over the dough with a grooved rolling pin or immediately cut out the cookies with a cookie cutter.
Remove excess dough. Bake the cookies for 5-6 minutes until the edges are golden. Completely cool and only after that remove them from the baking sheet.
Make a cup of coffee and enjoy it with fresh baked cookies.