How to Make It
Heat the oven to 450°. Put the squash on a large baking sheet and toss with the oil, 1/4 teaspoon of the salt, the pepper, and sage. Spread the squash out in a single layer. Roast, turning occasionally, until tender and starting to brown, 15 to 20 minutes.
In a small bowl, stir together the mascarpone, half-and-half, scallions, and the remaining 3/4 teaspoon salt.
Meanwhile, in a large pot of boiling, salted water, cook the penne until just done, about 13 minutes. Reserve 1 cup of the pasta-cooking water and drain. Return the pasta to the hot pan. Stir in the squash, mascarpone sauce, and ham. If the sauce seems too thick, add some of the reserved pasta-cooking water. Serve topped with the Parmesan.
Variations Instead of butternut squash, roast cubes of another winter squash, such as pumpkin or acorn squash—or try roasting cubed sweet potatoes.