1In large bowl, beat butter, shortening and sugar with electric mixer on medium speed until light and fluffy. Beat in vanilla and egg. On low speed, beat in flour, salt and baking powder until well combined. Beat in decors. Wrap dough in plastic wrap. Refrigerate 2 hours.
2Heat oven to 375°F. Place regular-size muffin cup pan upside down on cookie sheet. Spray pan with cooking spray.
3On work surface with rolling pin, roll dough until 1/8-inch thickness. With 4-inch round cutter, cut 8 rounds from dough. Place each dough round over muffin cup, smoothing dough and fixing any holes or cracks.
4Bake 10 to 12 minutes or until light golden brown. Cool cookie cups on muffin pan 10 minutes. Gently remove cookie cups from pan to cooling rack. Cool completely, about 15 minutes.