One-Pot Baked Pasta with Sausage and Broccoli Rabe

Place racks in center and upper third of oven; preheat to 325°. Heat a large pot of water over high. Add several tablespoons of salt and bring to a boil (this is for your pasta).

Grate 12 oz. Fontina cheese on the large holds of a box grater (you should have about 4½ cups). Smash 6 garlic cloves, peel, and coarsely chop. Pick all sage leaves from stems and set aside about 10. Finely chop remaining leaves (you should have about 1 Tbsp.). Trim tough dried ends from 1 bunch of broccoli rabe, then cut stems into 2" pieces. Leave leafy ends long.

Heat a deep, large, ovenproof skillet, preferably cast iron, over medium-high. Add ¼ cup oil and swirl to coat. Remove 1 lb. sausage from casings and add to skillet. Break into small pieces with a wooden spoon. Cook, undisturbed, until sausage is browned, about 4 minutes. Stir a couple of times and continue to cook, undisturbed again, until sausage is fully cooked through, about 3 minutes longer.

Add garlic, chopped sage, and ½ tsp. red pepper and cook, stirring, until garlic is golden, about 2 minutes.

Stir in 2 cups half-and-half and simmer until sauce is thickened slightly, about 2 minutes. Reduce heat to low.

Gradually add about two-thirds of cheese, bit by bit, stirring constantly and letting cheese melt completely before adding more, until sauce is smooth and thick, about 3 minutes; season with salt and remove from heat.

Meanwhile, cook 1 lb. pasta shells in boiling salted water 2 minutes shy of package instructions (8–10 minutes depending on type). During the last 2 minutes, add all of broccoli rabe to pot with pasta. Drain in a colander and shake several times to remove excess water. Return pasta and broccoli rabe to empty pasta pot.

Add cheesy sausage mixture from skillet to pot with pasta. Stir until pasta and broccoli rabe are coated in sauce, then transfer everything back to skillet.

Cover skillet tightly with foil and bake on center rack until pasta is tender and sauce is bubbling, 30–40 minutes. Let rest a few minutes while you heat broiler.

Remove foil and top with remaining cheese. Toss sage leaves with remaining 1 Tbsp. oil in a small bowl and arrange over pasta. Broil until cheese is browned and bubbling in spots, about 5 minutes (depending on strength of broiler).

Let pasta cool a minute or two before serving.