Cream together butter and sugar.
Stir in well-beaten egg, then milk and vanilla.
Combine flour, baking powder and salt.
Stir into creamed mixture.
Mix well.
Chill, covered in the fridge for at least 1/2 hour.
Roll dough out to 1/8" thick on a floured board.
Cut into shapes with cookie cutter.
Bake on a lightly greased baking sheet at 375F for 7-9 minutes.
Let cool a few minutes, then remove to a rack to finish cooling.
Decorate, if desired.
