6sliceswhite sandwich bread, or plain bread crumbs about 6 ounces, torn into rough pieces
3tablespoonsunsalted butter, cold, cut into 6 piece
Pasta and Cheese:
1poundelbow macaroni
5tablespoonsunsalted butter
6tablespoonsall-purpose flour
1 1/2teaspoonspowdered mustard
1/4teaspooncayenne pepper
5cupsmilk
8ouncesMonterey Jack cheese, shredded (2 cups)
8ouncessharp cheddar cheese, shredded (2 cups)
1teaspoontable salt
Instructions
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.
Bring a large pot of lightly salted water to a boil. Add the pasta and cook until pasta is tender. Drain pasta and set aside.
In a Dutch oven, heat butter over medium-high heat until foaming. Add flour, mustard, and cayenne 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. Take off of heat and whisk in cheeses and 1 teaspoon salt until melted. Add pasta and cook over medium-low heat, stirring constantly, until mixture is steaming and heated through, about 6 minutes.
Transfer mixture to broiler-safe 9 X 13-inch baking dish and sprinkle evenly with bread crumbs. Broil until crumbs are deep golden brown, 3 to 5 minutes, rotating pan if necessary for even browning. Cool about 5 minutes, then serve.