Preheat oven to 350°. In a large bowl, cream butter and sugar until light and fluffy. Beat in egg, food colouring and extract. In another bowl, whisk flour, cocoa, baking powder and salt; gradually beat into creamed mixture.
Shape dough into 1-in. balls. Place 1 in. apart on ungreased baking sheets. Press a deep indentation in center of each with the end of a wooden spoon handle.
Bake 9-11 minutes or until set. Remove from pans to wire racks to cool completely.
In a microwave, melt baking chips with oil; stir until smooth. Spoon a scant teaspoon filling into each cookie. Drizzle tops with remaining mixture. Sprinkle with peppermint candies. Let stand until set.