Combine first 4 ingredients in a large saucepan over low heat. Stir constantly until mixture is thick and glossy, about 9 minutes. Remove from heat; stir in vanilla. Chill for 4 hours or until firm enough to handle.
Shape into one-inch balls; roll in cocoa, nuts or crumbs. Chill until firm, about one hour. Store, covered, in the refrigerator.