Butter, softened at room temperature, beat with powdered sugar and salt.
Add the egg and mix well.
Add flour sifted with baking powder and mix again.
Form a dough ball, wrap it in plastic wrap and put in the refrigerator for 1-2 hours.
Remove dough from fridge, knead a little with your hands roll out on a floured table to a thickness of 1 cm Cut out circles with the diameter of your molds for muffins. By the way, without molds do not recommend cookies, it you just spread on the baking sheet.
Lay out mugs in forms. I have silicone molds, so I didn't grease them. If you have iron molds, I recommend to lubricate them with butter and a little sprinkle with flour.
Bake in a preheated 200 degree oven until Golden brown. It took me 12 minutes. Bon appetit.