1 1/2 cups sharp white cheddar cheese coarsely grated
1 cup gruyère, comte, jack, gouda, fontina, or raclette coarsely grated
1/2 cup pecorino romano cheese finely grated
1/4 cup all-purpose flour
3 cups milk any kind
1 1/2 cups milk or 1 12-ounce can evaporated milk
black pepper many grinds
1/8 teaspoon cayenne pepper or more to taste
freshly grated nutmeg a pinch or two
Kosher salt
Equipment
10-inch ovenproof skillet
Large bowl
Whisk
Directions
Heat oven to 375°F (190°C).
In a 10-inch ovenproof skillet, melt 2 tablespoons of butter over medium heat and add the breadcrumbs. Toast the crumbs in the butter, stirring, until light golden brown. Season with a pinch of salt and scrape crumbs into a dish to set aside. Clean the pan if desired.
Place uncooked pasta in a large bowl and cover with hot tap water. Soak for 10 minutes then drain, shaking off excess water.
Combine the three cheeses in a bowl.
Return the ovenproof skillet to the stove over medium-high heat and melt the remaining 3 tablespoons butter. Add the flour, whisking to combine. Add milk, 1/2 cup at a time, whisking to combine each addition with the butter-flour mixture until smooth. When all milk is added, season with kosher salt, black pepper, cayenne, and nutmeg. Cook, stirring, until mixture comes to a simmer and begins to thicken. Once simmering, cook for 2-3 minutes, stirring. Turn the burner off.
Set aside 2/3 cup of the cheese mixture, then add the rest of the cheeses to the sauce, stirring just until melted. Taste the sauce and adjust seasonings as needed. Stir in drained pasta until evenly coated. Sprinkle the surface with reserved cheese, followed by toasted breadcrumbs.
Transfer the skillet to the oven and bake, uncovered, for 30 minutes. If needed, bake an additional 5 minutes to soften. If more browning is desired, briefly use the broiler. Let rest for 2 to 3 minutes before serving.