COMBINE marshmallows and margarine in medium saucepan. Cook, stirring constantly, over medium heat for 1 to 2 minutes or until marshmallows are melted. Remove from heat; stir in cereal until coated. Press onto bottom of 13 x 9-inch baking pan coated with nonstick cooking spray, using spatula coated with nonstick cooking spray.
COMBINE margarine, sugar, evaporated milk and salt in medium, heavy-duty saucepan. Bring to a boil, stirring constantly, over medium heat. Cook, stirring constantly, for 4 1/2 to 5 minutes. Remove from heat. Add marshmallows, morsels and maple flavoring; stir vigorously for 1 minute or until marshmallows and morsels are completely melted. Pour over prepared crust. Sprinkle with nuts; press in slightly. Chill for 2 hours or until firm. Cut into squares.