Preheat oven to 350°. Cook macaroni in boiling water until almost tender; drain. Meanwhile, in a Dutch oven, melt butter over medium heat. Stir in flour, salt, mustard, pepper and pepper sauce until smooth. Cook and stir until bubbly, about 1 minute. Stir in cooked macaroni, milk and 4 cups cheese. , Transfer to an ungreased 13x9-in. baking dish. Cover and bake until bubbly, 45-50 minutes. Uncover; sprinkle with the remaining 1 cup cheese. Let stand for 5 minutes before serving.