Line 13x9-inch pan with foil, with ends of foil extending over sides. Spray with cooking spray. Melt 3/4 cup butter; mix with crumbs. Press onto bottom of pan.
Bring remaining butter, sugar, milk and marshmallows to boil in large saucepan on medium heat, stirring constantly. Cook and stir 5 min.
Add chocolate; cook until melted, stirring frequently.
Pour over crust.
Top with nuts and coconut. Refrigerate 2 hours or until firm.
