Tex-Mex Macaroni and Cheese

Heat the oven to 400°F and arrange a rack in the middle.Bring a large heavy-bottomed pot or Dutch oven of heavily salted water to a boil over high heat. Meanwhile, place the tortilla chips in a food processor fitted with a blade attachment and process into fine crumbs (you should have about 1 cup); set aside. (Alternatively, place the chips in a resealable plastic bag, press out the air, and seal the bag. Using a rolling pin, crush the chips into uniform fine crumbs.)

Add the pasta to the boiling water and cook according to the package directions or until just al dente.

Drain in a colander and rinse with cold water, making sure to stir the pasta while rinsing, until cooled and the shells are no longer sticking to each other; set aside in the colander.Dry the pot (no need to rinse), add 1 tablespoon of the butter, and place over medium-high heat until melted.

Add the chorizo and cook, breaking up the meat into small pieces with a wooden spoon, until cooked through, about 5 minutes.

Remove with a slotted spoon to a medium bowl; set aside.Reduce the heat to medium and add the remaining 4 tablespoons of butter. When the butter is melted, add the onion and cook, stirring occasionally, until softened, about 6 minutes.

Add the flour, measured salt, mustard, and cayenne and cook, stirring occasionally, until the flour has darkened slightly in color, about 2 minutes.While whisking constantly, slowly add the milk to the flour mixture until evenly combined and smooth. (It will get very thick when you first add the milk, then thin out.) Cook, stirring occasionally, until the mixture comes to a simmer and thickens slightly, about 8 to 10 minutes.

Add the cheeses and stir until completely melted and the sauce is smooth. Stir in the reserved pasta and chorizo and the jalapeños or green chiles and cook, stirring occasionally, until the pasta is heated through and steaming, about 4 to 6 minutes. Taste and season with salt as needed.

Transfer the mixture to a 13-by-9-inch baking dish and spread into an even layer.

Sprinkle with the crushed chips and bake until bubbling around the edges, about 20 minutes.

Remove to a wire rack and let cool for 5 minutes before serving.