Penne With Butternut Sage Sauce
- Process squash and onion in a food processor until finely chopped, about 1 minute.
- Heat butter in a 5- to 6-quart heavy pot over moderately high heat until foam subsides, then add sage and cook until fragrant, about 15 seconds.
- Add chopped squash mixture, water, salt, and pepper and simmer, uncovered, stirring occasionally, until water is evaporated and squash is very tender, 8 to 10 minutes.
- Stir in Parmigiano-Reggiano and remove squash mixture from heat.
- While squash mixture simmers, cook penne in a 6- to 8-quart pot of boiling salted water until al dente.
- Reserve 1 cup pasta cooking water, then drain pasta in a colander. Add 1/2 cup cooking water to squash mixture, then add drained pasta, tossing to combine.
- Thin sauce with additional cooking water as desired and serve pasta with additional cheese on the side.