1 Tbsp, plus 1/2 tsp kosher salt
8 oz mini farfalle pasta (or you can use small elbow macaroni)
5 Tbsp salted butter
2 cups coarse, fresh breadcrumbs (preferably homemade)
4 oz pecorino Romano or Parmesan cheese, finely grated (about 2 cups)
1 Tbsp finely chopped fresh sage leaves, plus 12 whole leaves
1 pound butternut squash, peeled, seeded and cut into 1/2-inch chunks
1 1/2 cups whole or reduced-fat milk
1 1/2 cups heavy cream
12 oz Gruyère cheese, coarsely grated (about 4 cups)
1/4 tsp cayenne pepper
Preheat the oven to 375°F. Butter an 8-inch square (1 1/2-quart) baking dish or pan (or six 8-ounce ramekins). Set aside.
Fill a 4- to 5-quart pot about three-quarters full with water and add 1 tablespoon of the salt. Bring to a boil and add the pasta. Cook, stirring once or twice, until tender but firm, 4 to 6 minutes. Drain, and reserve the pot.
In a medium skillet, melt 3 tablespoons of the butter. Turn off the heat and add the breadcrumbs and 1 cup of the pecorino. Stir to combine. Transfer to a small bowl and wipe out but do not wash the skillet.
Line a small plate with paper towels. Using the same skillet, melt the remaining 2 tablespoons butter over medium heat and cook just until it's starting to brown. Add the whole sage leaves and cook until the leaves are crisp and just beginning to darken, about 45 seconds. Remove the pan from the heat. Using tongs, transfer the leaves to the paper towel-lined plate and reserve both the leaves and the butter.
Using the same pot you used to cook the pasta, combine the squash, milk, cream, the remaining 1/2 teaspoon salt and the reserved sage butter. Cover and cook over medium-low heat, stirring occasionally and watching to make sure the cream mixture does not boil. Simmer the squash until it is very soft, 20 to 25 minutes. Cool slightly. Place about half of the mixture in a blender or food processor and purée. Put the purée back into the pot and repeat with the remaining squash.
Add the Gruyère, the remaining pecorino, the chopped sage, and the cayenne to the puréed squash mixture and stir until the cheese has melted (the heat of the squash mixture should melt it). Add the pasta and stir to combine.
Pour into the prepared baking dish, sprinkle with the bread crumb mixture, and place the fried sage leaves in a decorative pattern on top. Place the dish on a rimmed baking sheet and bake for 30 minutes, or until the mixture is brown and bubbly. Let cool for 15 minutes before serving.