Grease a 9-inch square baking pan; set aside. In large saucepan combine first 5 ingredients. Stir over low heat until blended. Over medium heat, bring to a full-rolling boil being careful not to mistake escaping air bubbles for boiling. Boil slowly, stirring constantly, 5 minutes. Remove from heat, stir in peanut butter until blended. Turn into greased pan and cool.