1. Prepare crust, if desired.
2. Combine sugar, cocoa, cornstarch and salt in medium saucepan; gradually stir in milk. Cook over medium heat, stirring constantly, until mixture comes to full rolling boil; boil and stir 1 minute. Remove from heat; stir in butter and vanilla. Pour into prepared crust; carefully press plastic wrap directly onto pie filling. Cool; refrigerate 6 hours or until firm.
3. Shortly before serving, remove wrappers from peppermint patties. Remove plastic wrap from pie. Cut 9 peppermint candies in half; place, cut side down, at outer edge of pie filling, forming a scalloped edge. Finely chop remaining 9 patties; fold into whipped topping with green food color, if desired. Spread peppermint topping on pie. Serve immediately. Cover; refrigerate leftover pie. 10 servings.