This is my fav American style Mac and cheese:
Make a bechamel sauce using a ratio of 1 tbsp of flour and 1 tbsp of butter per cup of milk (so if you want to make 3 cups, you use 3 tbsp of flour and butter each). Melt the butter in a saucepan. Add the flour and cook for a couple of minutes stirring continuously. Take the pan off the heat and whisk in the milk. Return the pan to the heat (med-high) and continue stirring until the sauce thickens and starts to bubble.
Add a few handfuls of cheese such as cheddar, colby, parma, swiss etc. and stir on low heat until the cheese melts. Season to taste and add nutmeg if you want.
Mix the sauce with your choice of cooked pasta (I like shells instead of traditional macaroni) and pour into a baking dish. Top with breadcrumbs and cheese and put it under the grill of a few minutes until the cheese is melted and breadcrumbs golden.
Optional additions include cooked bacon, chicken and broccoli, cut up hot dogs... Or basically anything you like!
Healthy option- make a smaller portion of bechamel sauce than you need and add some puréed cauliflower when you add the cheese. I like a 1 to 1 ration (eg bechamel sauce made with 1 cup of milk = 1 cup of cauliflower purée)
Im hungry just writing this...