Step 1

Preheat oven to 375 degrees. Using a large, sharp knife, trim ends; halve squash crosswise to separate bulb from neck. Peel with a vegetable peeler. Cut both pieces in half lengthwise. With a spoon, scoop out seeds; discard.

Step 2

Cut squash into 2-inch chunks; transfer to a small rimmed baking sheet. Toss with oil and sage; season generously with salt and pepper. Scatter garlic around squash. Roast until squash is very tender, about 40 minutes, tossing once halfway through. Remove and discard skin from garlic.

Step 3

Transfer squash and garlic to a food processor; puree. With motor running, add half-and-half through the feed tube; process until smooth. Add 1 to 2 cups water; continue to process until smooth, adding water to thin if necessary. Season again generously with salt. (To freeze, see below.)

Step 4

Cook pasta according to package instructions. Reserve 1 cup pasta water; drain pasta and return to pot. Pour sauce over pasta; toss to coat. Add some pasta water to thin sauce if necessary. Serve with desired toppings.