K&A's Valentine's Day Mac' n' Cheese

Ingredients

• 6 slices good-quality white bread, crusts removed, torn 1/2-inch pieces
• 4 tablespoons (1 stick) unsalted butter, plus more for dish
• 5 cups milk
• 1/2 cup all-purpose flour
• 2 teaspoons kosher salt
• 1/4 teaspoon freshly grated nutmeg
• 3/4 teaspoon garlic powder
• 1/2 teaspoon onion powder
• 1/2 teaspoon freshly ground black pepper
• 3/4 teaspoon cayenne pepper
• 1/2 pound Canadian bacon or smoked ham, cubed (optional)
• 4 1/2 cups (about 18 ounces) grated sharp white cheddar
• 2 cups (about 8 ounces) grated Gruyere or 1 1/4 cups (about 5 ounces) grated pecorino Romano
• 1 pound elbow macaroni (4 cups dry)

Method

• 1. Butter a 3-quart casserole dish; set aside. Place bread pieces in a medium bowl. In a small saucepan over medium heat, melt 2 tablespoons butter. Pour butter into the bowl with bread, and toss. Set the breadcrumbs aside. 
• 2. In medium saucepan heat 4 cups of milk over medium heat. Mix remaining 1 cup cool milk and flour. Melt remaining 2 tablespoons butter in a medium sauce pan over medium heat. When butter bubbles, add milk and flour mixture. Cook, stirring, 1 minute.
• 3. Slowly pour hot milk into flour-butter mixture while whisking. Continue cooking, whisking constantly, until the mixture bubbles and becomes thick.
• 3a. While cheese mixture is thickening, fill a large saucepan with water. Bring to a boil. Add macaroni; cook 2 to 3 fewer minutes than manufacturer's directions, until outside of pasta is cooked and inside is underdone. Transfer the macaroni to a colander, rinse under cold running water to halt cooking process, and drain well. 
• 4. Set heat to low under sauce pan with milk mixture. Stir in salt, nutmeg, onion powder, garlic powder, black pepper, cayenne pepper, 3 cups cheddar, 1 1/2 cups Gruyere or 1 cup pecorino Romano and ham. Set cheese sauce aside.
• 5. Stir macaroni into the reserved cheese sauce.
• 6.  Heat the oven to 375 degrees. Pour the mixture into the prepared casserole dish. Sprinkle remaining 1 1/2 cups cheddar and 1/2 cup Gruyere or 1/4 cup pecorino Romano; scatter breadcrumbs over the top. 
• 7. Place cookie sheet under casserole dish and bake until browned on top, about 45 minutes. 
• 8. Transfer dish to a wire rack to cool for 5 minutes; serve.

Adapted from: marthastewart.com