Butter a 13- X 9-inch baking dish. In medium saucepan bring broth and butter to boil. Add polenta; cook and stir over low heat 10 minutes. Add remaining ingredients and cook 5 minutes more. Pour into baking dish and chill at least 1 hour. Cut into 2-inch squares or diamonds. Serve at room temperature or grill a minute or two on each side. Makes 24 appetizers.