When making a cheese sauce that starts with a bechamel, is there a specific way to add cheese so that it won't break easily when it cools? Basically, if I'm making mac and cheese for a potluck dinner, I was wondering what the best way to make the sauce would be so that it held up longer.
A bechamel with cheese added is usually called a mornay, and there are many versions of it. The cheese can vary from harder cheeses such as parmesan to softer cheddars, gruyere or Swiss. The important point in adding the cheese is to grate it and then add it in batches after you've made the sauce, stirring well to make sure it is melted before you add more.
For your macaroni and cheese, I'd make the sauce and combine it with the cooked pasta. Then you could freeze it before baking, or you could bake it, cool it and freeze it, then reheat it before the dinner.