Bring a large pot of salted water to a boil and cook pasta until just al dente. Drain and set aside.

In a saucepan, melt butter over medium heat. Whisk in flour to form a roux.

Gradually whisk in warm milk and cream until smooth and slightly thickened.

Lower the heat and add shredded cheeses in small handfuls, stirring until melted and creamy.

Season with mustard powder, nutmeg, black pepper, and optional hot sauce.

Fold pasta into the sauce until well coated.

For stovetop version: serve immediately with garnish.

For baked version: transfer to a baking dish, top with breadcrumbs, and broil until golden.