Sift together flour, baking powder, and salt. Set aside. Place butter and sugar in large bowl of electric stand mixer and beat until light in color. Add egg and milk and beat to combine. Put mixer on low speed, gradually add flour, and beat until mixture pulls away from the side of the bowl. Divide the dough in half, covered and refrigerate for 30 minutes.

Sprinkle a flat working surface with powdered sugar. Working on the dough one at a time. Sprinkle rolling pin with powdered sugar, and roll out the dough to 1/4-inch thick. Cut into desired shapes, place the sugar cookies 1-inch apart on a baking sheet.

Bake the sugar cookies for 7 to 9 minutes or until cookies are just beginning to turn brown around the edges, rotating cookie sheet halfway through baking time. Let sit on baking sheet for 2 minutes after removal from oven.

Let cool on on wire rack. Serve as is or decorate with cookie icing, sprinkles or nonpareil. Store the sugar cookies in airtight containers for up to 1 week.