Combine melted butter, cocoa, sugar, eggs, and vanilla in large mixing bowl.
Using mixer on low/medium mix thoroughly.
Stir in flour, salt, and nuts then pour in greased 9X13 baking pan.
Bake at 350 degrees for 30-35 minutes.
Remove from oven, pour small pkg of marshmallows over top of cake.
Cover with aluminum foil for 7 min, then frost.