In a small bowl, cream butter and confectioners’ sugar until light and fluffy, 3-4 minutes. Beat in extract. In another bowl, whisk flour and cornstarch; gradually beat into creamed mixture. Refrigerate, covered, 30 minutes or until firm enough to handle.
Preheat oven to 350°F. Shape dough into 1-in. balls; place 2 in. apart on ungreased baking sheets. Bake 9-11 minutes or until bottoms are light brown. Remove from pans to wire racks to cool completely.
In a small bowl, beat butter until creamy. Beat in milk, extract and, if desired, food coloring. Gradually beat in confectioners’ sugar until smooth. Spread over cookies; sprinkle with crushed candies. Store in an airtight container.
