1In medium bowl, mix flour, cocoa, baking powder and salt; set aside. In large bowl, beat 1 cup of the butter and the granulated sugar with electric mixer on medium speed 3 minutes or until creamy. Add egg and peppermint extract; beat until well blended. Gradually beat in flour mixture. Divide dough in half. On 2 sheets of plastic wrap, shape each half into 13x1 1/2-inch log. Wrap tightly; freeze 2 hours.
2Heat oven to 325°F. Spray cookie sheets with cooking spray. Cut each log into 32 (about 1/4-inch) slices. On cookie sheets, place slices 1 inch apart. Bake 12 to 13 minutes or until set. Cool 1 minute; remove from cookie sheets to cooling racks. Cool completely.
3In large bowl, beat remaining 1/3 cup butter and the cream cheese with electric mixer on medium speed until creamy. Gradually beat in powdered sugar. For each sandwich cookie, spread about 2 teaspoons filling on bottom of 1 cookie. Top with second cookie, bottom side down; gently press together. Roll sides of sandwich cookies in crushed candies.