FOR CHOCOLATE LAYER:
HEAT 1/3 cup morsels and butter in small saucepan over low heat stirring frequently, until morsels are melted. Spread melted chocolate on bottom and up sides of prebaked pie shell. Refrigerate for 15 minutes or until set.
FOR CARAMEL LAYER:
HEAT caramels and 1/3 cup whipping cream in small saucepan over medium heat, stirring frequently, until caramels are melted and mixture is smooth. Stir in nuts. Spoon over chocolate layer; cover. Refrigerate.
FOR MARSHMALLOW LAYER:
HEAT 1 1/3 cups morsels, milk and marshmallows in medium saucepan over low heat, stirring constantly, until chocolate and marshmallows are melted and mixture is smooth. Remove from heat. Stir in vanilla extract. Cool completely.
BEAT remaining whipping cream until soft peaks form; fold into cooled marshmallow mixture. Carefully spoon over caramel layer (pie will be full). Refrigerate for 3 hours or overnight.
HEAT 3 caramels, 2 tablespoons whipping cream and 1 tablespoon butter in small saucepan over low heat, stirring frequently, until smooth; cool slightly. Top each serving with topping, whipped cream and remaining morsels.