Combine milk and pudding mix in a medium saucepan, stirring well with a whisk. Cook over medium heat 8 minutes or until mixture comes to a boil, stirring constantly. Remove from heat, and add chocolate chips, stirring until chocolate melts. Place pan in an ice-water bath for 5 minutes or until cool, stirring often.
Pour filling into crust. Cover surface of filling with plastic wrap, and chill at least 3 hours. Spread whipped topping over pie before serving.