All-Time Favorite Sugar Cookies

Directions

1. Whisk together flour, baking powder and salt. In a small bowl, beat egg whites on high speed until stiff but not dry. In a large bowl, beat egg yolks on high until thick, about 2 minutes. Fold in whites. Add melted margarine, sugar and vanilla; beat until blended. Stir in flour mixture.
2. Divide dough in half; shape each into a disk. Wrap in plastic; refrigerate until firm enough to roll, 4 hours or overnight.
3. Preheat oven to 350°. On a lightly floured surface, roll each portion of dough to 1/4-in. thickness. Cut with floured 2-in. cookie cutters. Place 2 in. apart on greased baking sheets.
4. Bake until edges are light brown, 7-9 minutes. Cool completely on wire racks.
5. For frosting, beat butter until creamy; gradually beat in confectioners' sugar until smooth. Beat in 5 tablespoons milk and vanilla until light and fluffy; thin with additional milk if desired. Spread or pipe onto cookies. If desired, decorate with sprinkles.