While macaroni is cooking, melt 1/2 cup butter in 5-quart Dutch oven over medium heat. Stir in flour, salt, pepper and red pepper. Cook over medium heat, stirring constantly, until mixture is smooth and bubbly, then cook 1 minute longer. Stir in mustard and Worcestershire sauce. Stir in milk. Heat to boiling, stirring frequently. Boil and stir 1 minute. Remove from heat; stir in cheese until melted.