1. Heat oven to 350°F.
2. Beat butter, shortening and sugar until well blended. Beat in egg and vanilla. Stir together 2 cups flour, baking powder and salt. Gradually beat into butter mixture.
3. Divide dough mixture into halves. Add remaining 2 tablespoons flour to one half and cocoa to the other half, blending well. Roll dough into 1-inch balls. (Roll together a pinch of vanilla dough and a pinch of chocolate dough for marbled cookies.) Place balls on ungreased cookie sheets.
4. Bake 9 to 11 minutes or until cookies are set. Remove from oven to wire rack. Cool 1 minute. Press candy piece into center of each cookie. Remove from cookie sheet to wire rack; cool completely.
Makes about 48 cookies.