1. Heat oven to 350°F. Beat shortening and peanut butter in large bowl until well blended. Add brown sugar and 1/3 cup granulated sugar; beat until fluffy. Add egg, milk and vanilla; beat well. Stir together flour, cocoa, baking soda and salt; gradually beat into peanut butter mixture.
2. Shape dough into 1-inch balls. Roll in decorator's sugar; place on ungreased cookie sheet.
3. Bake 8 to 10 minutes or until set. Cool 3 minutes; press 1 to 2 mini peanut butter cups into center of each cookie. Cookies may crack around edges. Remove from cookie sheet to wire rack. Cool completely. Makes about 48 cookies.