Mix 1st 5 ingredients well in a large heavy saucepan. Cook over medium high, stirring constantly, 15-20 min. It is done when it is very thick and leaves side of pan, forming a ball in the center as you stir. Turn onto a buttered baking sheet. Cover loosely with foil or plastic wrap. Let cool completely. Lightly butter hands. Shape candy into balls. Roll in nuts. Top with cherry half if desired. Cover, store in refrigerator. Yield 2 1/2 dozen.