If you'll be baking, preheat the oven to 350 F. In a large stockpot, bring salted water to a boil for cooking the pasta.

While waiting for the pasta water to boil, melt the butter in a large saucepan. Add the flour and cook, stirring occasionally, for 10 minutes.

Stir in the milk gradually and bring to boil. Reduce to simmer and cook for 15 minutes.

While the sauce is simmering, boil the macaroni in the salted water until al dente, according to package directions.

While the pasta is cooking, stir the cheeses into the sauce until fully melted and remove from the heat.

When the pasta has finished cooking, drain it in a colander and add it to the cheese sauce. Mix to combine.

Pour it into a 9 x 13 inch baking dish and bake for 30 minutes (for kids who don't like "crusty" macaroni and cheese, this need not go in the oven).

Allow to cool slightly and serve hot.