Mix cookie crumbs and margarine; press onto bottom and up side of 9-inch pie plate.
Bake 10 min.; cool.
Microwave caramels and half-and-half in medium microwaveable bowl on HIGH 3 min. or until caramels are completely melted, stirring after 1-1/2 min. Stir in nuts; spread onto bottom of crust. Refrigerate 10 min. or until set. Chop 2 oz. chocolate; sprinkle over caramel layer in crust.
Microwave remaining chocolate in separate microwaveable bowl 30 sec.; stir until completely melted.
Drizzle over pie. Refrigerate 1 hour or until chocolate is firm.