Best Potluck Macaroni and Cheese

From the episode: Barbecued Chicken
So many macaroni and cheese recipes slump into a runny mess. Our baked mac and cheese is creamy, sturdy, and rich.
Serves 8 to 10.
Use block American cheese from the deli counter—prewrapped slices of American cheese will result in a drier mac and cheese.
Ingredients
3–4 slices hearty white sandwich bread , torn into large pieces
8 tablespoons unsalted butter , 4 tablespoons melted
1/4 cup grated Parmesan cheese
Salt
1 pound elbow macaroni
5 tablespoons all-purpose flour
3 (12-ounce) cans evaporated milk
2 teaspoons hot sauce
1/8 teaspoon ground nutmeg
1 teaspoon dry mustard
2 cups shredded extra-sharp cheddar cheese
1 1/4 cups shredded American cheese , (about 5 ounces)
3/4 cup shredded Monterey Jack cheese
Instructions
• 1. Adjust oven rack to middle position and heat oven to 350 degrees. Pulse bread, melted butter, and Parmesan in food processor until ground to coarse crumb. Transfer to bowl.
• 2. Bring 4 quarts water to boil in large pot. Add 1 tablespoon salt and macaroni to boiling water and cook until al dente, about 6 minutes. Reserve 1/2 cup macaroni cooking water, then drain and rinse macaroni in colander under cold running water. Set aside.
• 3. Melt remaining 4 tablespoons butter in now-empty pot over medium-high heat until foaming. Stir in flour and cook, stirring constantly, until mixture turns light brown, about 1 minute. Slowly whisk in evaporated milk, hot sauce, nutmeg, mustard, and 2 teaspoons salt and cook until mixture begins to simmer and is slightly thickened, about 4 minutes. Off heat, whisk in cheeses and 1/2 cup reserved pasta water until cheese melts. Stir in macaroni until completely coated.
• 4. Transfer mixture to 13 by 9-inch baking dish and top with bread crumb mixture. Bake until cheese is bubbling around edges and top is golden brown, 20 to 25 minutes. Let sit for 5 to 10 minutes before serving.
• Make Ahead: The macaroni and cheese can be made in advance through step 3; since the pasta continues to absorb moisture, adjustments must be made to avoid a dry filling. To do so, increase amount of reserved pasta cooking water to 1 cup. Pour filling into 13 by 9-inch baking dish, lay plastic wrap directly on surface of pasta, and refrigerate for up to 1 day. The bread crumb mixture may be refrigerated in airtight container up to 2 days. When ready to bake, remove plastic wrap, cover macaroni mixture with foil, and bake for 30 minutes. Uncover, sprinkle bread crumbs over top, and bake until topping is golden brown, about 20 minutes longer.