Begin by creaming the softened butter with confectioners' sugar in a small mixing bowl until the mixture becomes light and fluffy, approximately 3 to 4 minutes. Incorporate the peppermint extract into the creamed mixture. In a separate bowl, combine the all-purpose flour and cornstarch, then gradually add this dry blend to the creamed mixture. Cover and refrigerate the dough for 30 minutes or until it is firm enough to handle.

Preheat your oven to 350°F (175°C). Form the chilled dough into balls measuring about 1 inch in diameter and arrange them on ungreased baking sheets, spacing them 2 inches apart. Bake in the preheated oven for 9 to 11 minutes, or until the bottoms of the cookies are lightly browned. Once baked, transfer the cookies to wire racks to cool completely.

For the frosting, beat the softened butter in a small bowl until creamy. Gradually mix in the milk and peppermint extract, adding food coloring if desired. Slowly incorporate the confectioners' sugar until the frosting achieves a smooth consistency. Spread the frosting generously over the cooled cookies, then top with crushed peppermint candies. Store the finished meltaways in an airtight container to maintain their freshness.