As I said before, the macaroni that are normally used to make this recipe for Mac & Cheese are the pasta elbows what they call elbows. We heat a pot with salty water, to cook the pasta in it, that we will leave a point harder than al dente to finish cooking them in the oven, which we will also preheat to 200ºC.
While the pasta is cooking, we will prepare the sauce for the macaroni, a kind of bechamel made with milk and corn flour. To do this, in a frying pan, we mix that flour diluted in a little cold milk and then we add the rest of the milk, the teaspoon of mustard, a pinch of salt and another of pepper. Mix well and heat over medium heat.
It is very important not to stop stirring while we heat, until the sauce binds. When the milk has heated up a little, add the butter, stirring well, until the sauce becomes a thick cream. Then we lower the heat to a minimum and add the cheddar cheese, stirring again until it is incorporated.
When the pasta is cooked, we mix it with the sauce and place it in a baking dish. Cover with the grated Parmesan cheese and bake in the middle-high part for 15 minutes, then gratin another three minutes, until well browned on top. We serve by warning diners of the interior temperature, to avoid burns.