In a large saucepan, combine sugar and cocoa; stir in milk. Add butter. Bring to a boil over medium heat; cook and stir until sugar is dissolved. Add marshmallows; cook until melted. Remove from the heat stir in vanilla. Serve with ice cream. Top with nuts and cherries if desired. Yield: 2 cups, 16 servings, 2 tablespoons per serving.