Cook's Illustrated Classic Macaroni and Cheese Recipe

Directions:

1. For the bread-crumb topping: Pulse bread and butter in food processor until crumbs are about 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.
3. Bring 4 quarts water to boil in Dutch oven over high heat.
4. Add macaroni and 1 tablespoon salt. Cook until pasta is tender. Drain pasta and set aside in colander.
5. In now-empty Dutch oven, heat butter over medium-high heat until foaming.
6. Add flour, mustard, and cayenne and whisk well to combine.
7. Continue whisking until mixture becomes fragrant and deepens in color, about 1 minute.
8. Gradually whisk in milk and bring mixture to a boil, whisking constantly (mixture must reach full boil to fully thicken).
9. Reduce heat to medium and simmer, whisking occasionally, until thickened to consistency of heavy cream, about 5 minutes.
10. Off heat, whisk in cheeses and 1 teaspoon salt until cheeses are fully melted.
11. Add pasta and cook over medium-low heat, stirring constantly, until mixture is steaming and heated through, about 6 minutes.
12. Transfer mixture to broiler-safe 13x9 inch baking dish and sprinkle evenly with bread crumbs.
13. Broil until crumbs are deep golden brown, 3 to 5 minutes, rotating pan if necessary for even browning.
14. Cool about 5 minutes, then serve.