If you like a mellow-flavored mac and cheese, don't add the extra 2 cups cheese; instead, add an extra tablespoon of flour to thicken the sauce. This recipe is easily doubled. To fill a large casserole or 9" x 13" x 2" pan, double all ingredients, EXCEPT those for the crumb topping. Or, for a more generous crumb topping, feel free to double those ingredients, too. Recipe Source: King Arthur Flour