Butter 13x9-inch pan; set aside.
Combine all ingredients except vanilla in heavy 4-quart saucepan. Cook over medium heat, stirring occasionally, 15-20 minutes or until butter is melted and mixture comes to a boil.
Continue cooking, 25-30 minutes or until candy thermometer reaches 244°F or small amount of mixture dropped into ice water forms a firm ball.
Remove from heat; stir in vanilla. Pour into prepared pan. Cool completely.
Cut into 1 1/2x1-inch pieces; wrap candies in plastic food wrap. Store refrigerated.