2 oz. unsalted butter
12 large conchiglie pasta shells
4 cups Italian ground duck sausage, or substitute Italian sausage
2 cups 1-inch-dice butternut squash
1 cup packed blanched broccoli spigarello (or substitute any other winter greens except collards), squeezed dry in a kitchen towel and chopped
1½ cups freshly grated Parmesan cheese
Kosher salt and freshly ground black pepper
Melt the butter in a small saucepan over low heat. Increase the heat to medium and cook the butter until the milk solids brown, three to four minutes. Remove immediately and set aside.
Bring a pot of heavily salted water to boil over high heat. Add the pasta and cook until al dente, seven to 10 minutes. Drain but do not rinse.
Sauté the sausage in a skillet over medium heat until cooked through. Using a slotted spoon, transfer the sausage to a large bowl, reserving the fat in the skillet. Increase the heat to medium-high, add the squash, and cook, stirring frequently, until tender, eight to 10 minutes. Add the squash, greens, and one cup of the Parmesan cheese to the bowl with the sausage. Season with salt and pepper.
Fill the shells with the warm mixture and arrange three on each plate. Drizzle with brown butter and sprinkle with the remaining Parmesan cheese.