In separate bowl, sift the baking powder, salt and flour. Add to wet ingredients slowly until thoroughly combined.
Cookie dough must be chilled until firm, or overnight.
Remove dough from fridge and roll out to a 1/4-inch thickness.
Preheat oven to 400 degrees.
With cookie cutters or rim of drinking glass, cut out cookies.
Place cookies on an ungreased cookie sheet and bake in preheated oven for 8-10 minutes, depending on oven. Check often to prevent over cooking or burning. Cool on baking rack when done.
Meanwhile, prepare frosting - it's a MUST for these cookies! (go all the way or not at all)
Cream butter, milk and vanilla together.
Slowly add powdered sugar to butter until desired consistency. If you'd like, add liquid food coloring for festive cookies. Note: I had some trouble with the icing and needed to add a little more milk to thin it out and make it spreadable, but I may have done something wrong ;-)
When cookies are cooled, slather this heavenly frosting. For more texture and color, press the top of the cookie in sprinkles, colored sugar or just eat plain!