Beat butter and shortening in a large mixing bowl with an electric mixer on medium to high speed for 30 seconds. Add sugar, baking powder, and salt; beat until combined. Beat in egg, milk, and vanilla, scraping sides of the bowl occasionally. Beat in as much flour as you can with the mixer; stir in remaining flour with a wooden spoon. Divide dough in half. Cover and chill about 3 hours or until dough is easy to handle.
Heat oven to 350 degree F. Roll each dough half on a lightly floured surface into a 12x9-inch rectangle. Cut each rectangle into twelve 3-inch squares using a sharp knife or a fluted pastry wheel. Place squares 2 inches apart on an ungreased cookie sheet. Sprinkle each with about 1 teaspoon crushed candy and about 1/2 teaspoon red decorating sugar; gently press into dough.
Cut 1-inch slits from each corner toward the center of each square. Fold every other tip to the center to form pinwheels, pressing lightly to seal the tips. Tuck a crafts stick into each pinwheel, pressing dough around stick. Sprinkle with additional crushed candy and red decorating sugar.
Bake for 7 to 8 minutes or until edges begin to brown. Cool for 1 minute. Transfer to wire racks and cool completely. (Do not lift by sticks until completely cooled.) Makes 24 spinwheels.