- 1 pound cavatappi (ridged corkscrew pasta) or penne rigate
- 1 3/4 pounds butternut squash, peeled, seeded, and cut into 1-inch pieces (about 3 1/2 cups)
- 3 garlic cloves, finely chopped
- 1 tablespoon olive oil
- 1 cup water
- 1 teaspoon finely chopped fresh sage
- 1/2 teaspoon salt
- 3 tablespoons unsalted butter, cut into 1/2-inch cubes
- 2 ounces finely grated Parmigiano-Reggiano (1 cup) plus additional for sprinkling
- Cook pasta in a 6- to 8-quart pot of boiling salted water until al dente.
- While heating water for pasta, pulse squash in a food processor until coarsely chopped. Cook garlic in oil in a 12-inch heavy skillet over moderate heat, stirring, until pale golden, about 1 minute. Add squash, water (1 cup), sage, and salt and simmer, covered, until squash is tender, 5 to 7 minutes. Add butter and stir until incorporated.
- Reserve 1 cup pasta-cooking water, then drain pasta and return to pot. Stir in squash mixture, cheese, and pepper to taste until combined well. Season with salt and add some of reserved cooking water to moisten if necessary.