In 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.