Combine sugar, butter, eggs and vanilla. Beat at medium speed until light and fluffy. Add flour, cocoa, baking powder and salt. Beat at low until soft dough forms. Stir in mints. Cover with plastic wrap. Chill 2-3 hours.
Heat oven to 375 degrees. Lightly grease cookie sheets. Shape dough into 1 balls. Place 2 apart on prepared cookie sheets. Bake 8-10 minutes. Cool completely.
In 1 qt. saucepan, combine candy coating and shortening. Melt over low heat stirring constantly. Stir in food coloring. Pipe or drizzle glaze over cookies to form stripes. Let dry completely before storing.