1. combine butter, sugar, milk in large pan. Stir until dissolved. Stir a few times until boils. Cover and let boil 5 minutes with 3 stirrings.
2. Remove from heat, add marshmellows, stir until dissolved, add vanilla and nuts. Add chocolate 1 at a time. Stir until dissolved. Pour in greased pan- (1) 10 x 15 pan or (2) 13 x 9 pans.
3. May or may not leave refrigerated.