One-Pot Broccoli Mac and Cheese

Toss together 12 oz. Monterey Jack, coarsely grated (about 3 cups), and 12 oz. sharp cheddar, coarsely grated (about 3 cups), in a large bowl with your hands. Sprinkle 2 Tbsp. cornstarch over and toss again until cheese is evenly coated. Set cheese mixture aside.

Bring 5 cups water to a boil in a large Dutch oven or other heavy pot. Add 1 lb. lumache (snail shells) or other medium shell pasta and cook, stirring often to keep pasta from sticking to bottom of pot, until about half of the water has been absorbed and pasta is very al dente, 7–9 minutes for most pasta shapes (about 3 minutes less than package directions).

Add one 1-lb. bag or two 10–12.6-oz. bags frozen broccoli florets and 2½ cups whole milk to pot and return to a boil. Cook, stirring often, until pasta and broccoli are both tender but not mushy, 2–3 minutes. (Taste a piece of pasta to check.)

Reduce heat to low and mix in 1 tsp. English mustard powder, 1 Tbsp. plus 1 tsp. Diamond Crystal or 2¼ tsp. Morton Kosher salt, and 1 tsp. freshly ground black pepper. Add reserved cheese mixture a handful at a time, stirring after each addition until mostly melted before adding more.

Remove pot from heat. Taste broccoli mac and cheese and season with more salt and pepper if needed. Let sit, stirring occasionally, until cheese sauce has thickened slightly before serving, 5–10 minutes.