Serves 6 to 8, or 10 to 12 as a side.
It's crucial to cook the pasta until tender--just past the "al dente" stage. In fact, overcooking is better than undercooking the pasta. Whole, low fat, and skim milk all work well in this recipe. The recipe can be halved and baked in an 8-inch-square, broiler safe baking dish. If desired, offer celery salt or hot sauce (such as Tabasco) for sprinkling at the table.
6 slices white sandwich bread (good-quality, about 6 ounces), torn into rough pieces
3 T. unsalted butter (cold), cut into 6 pieces
1 lb. elbow macaroni
1 T. table salt
5 T. unsalted butter
6 T. flour
1 ½ tsp. powdered mustard
¼ tsp. cayenne pepper (optional)
5 cups milk
8 oz. Monterey jack cheese, shredded (2 cups)
8 oz. sharp cheddar cheese, shredded (2 cups)
1 tsp. table salt
1. For the bread crumbs: Pulse bread and butter in food processor until crumbs are no larger than 1/8 inch, ten to fifteen 1-second pulses. Set aside.
2. For the pasta and cheese: Adjust oven rack to lower-middle position and heat broiler. Bring 4 quarts water to boil in Dutch oven over high heat. Add macaroni and 1-tablespoon salt; cook until pasta is tender. Drain pasta and set aside in colander.
3. In now-empty Dutch oven, heat butter over medium-high heat until foaming. Add flour, mustard, and cayenne (if using) and whisk well to combine. Continue whisking until mixture becomes fragrant and deepens in color, about 1 minute. Gradually whisk in milk; bring mixture to boil, whisking constantly (mixture must reach full boil to fully thicken). Reduce heat to medium and simmer, whisking occasionally, until thickened to consistency of heavy cream, about 5 minutes. Off heat, whisk in cheeses and 1 teaspoon salt until cheeses are fully melted. Add pasta and cook over medium-low heat, stirring constantly, until mixture is steaming and heated through, about 6 minutes.
4. Transfer mixture to broiler-safe 9-by 13-inch baking dish and sprinkle evenly with breadcrumbs. Broil until crumbs are deep golden brown, 3 to 5 minutes, rotating pan if necessary for even browning. Cool about 5 minutes, then serve
