Method
Heat the oven to 375°F. Boil the macaroni in salted water until just under al dente; drain.
Melt the butter in a saucepan, whisk in the flour, and cook for 2 minutes. Gradually whisk in the warm milk and simmer until thickened.
Remove from the heat, stir in the mustard and cheeses until smooth, and season. Fold in the pasta and spread in the baking dish.
Mix the breadcrumbs with oil or butter, scatter on top, and bake until bubbling and browned, 20–25 minutes.
Notes
Slightly undercook the pasta so it finishes in the sauce rather than becoming soft.
Related recipes and techniques
These are extensions, technique comparisons, or serving relationships; the complete recipe above remains usable as written.
- The cheese sauce uses the roux-and-milk structure of Béchamel Mother Sauce, then adds cheese to become a Mornay-style sauce; the complete method above remains self-contained.