In large bowl with mixer at med speed, beat butter & sugar until light & fluffy; beat egg in well. At low speed beat in flour & baking powder until well blended. Flatten dough to disk shape; refrigerate, wraped in plastic wrap, 1 hour until firm. Heat oven to 375. Work with half dough at a time; keep remainder refrigerated. Mold or press into shapes; or roll out to 1/8" or 1/4" thick between two sheets of wax paper or plastic wrap & cut into desired shapes. Place shapes on ungreased cookie sheets, spacing about 1" apart. Bake 8-15 minutes depending on thickness of dough, until firm to touch & edges are lightly browned. Cool on racks. Store in airtight containers.