Pumpkin Gnocchi With Parmesan, Sage and Truffles

1.
Preheat the oven to 400°F. Remove the stem, if present, from the squash or pumpkin, then slice between the vertical grooves to produce thick, half-moon slices. Scrape out and discard the seeds and strings. Place the squash on their sides in one layer on a large baking sheet. Roast until a knife easily pierces the flesh, about 25 minutes. Let cool slightly. When cool enough to handle, scrape the flesh from the skin into a sieve. Using a rubber scraper or spatula, work the squash through the sieve into a bowl. Measure 1 1/2 cups of squash puree. 2.
Transfer the puree to a medium saucepan and add the water, salt, and nutmeg. When it begins to boil, add a cup of the flour, a little at a time, stirring constantly. Reduce the heat to medium and cook, stirring constantly, until the mixture pulls together as a smooth, bright orange ball, about 10 minutes. Remove from the heat and beat in the egg, then 1 1/2 cups of the cheese. Turn out onto a clean work surface and let cool slightly. When cool enough to handle, knead the remaining 1/2, cup flour into the dough to form a smooth ball. Divide the dough into eight pieces and roll each into a 1/2-inch-thick log, dusting the work surface with flour as necessary to prevent sticking. Cut the logs into 1-inch-long segments. Spread some flour on a baking sheet, add the gnocchi, and shake to lightly coat. Set aside until ready to cook. The gnocchi can be stored, covered, and refrigerated, for up to a day. 3.
To prepare the sauce, in a large skillet, pour extra virgin olive oil into pan on very low heat. Add the sage and cook until it starts to crisp, 3 to 5 minutes. Set aside. 4.
Bring a large pot of water to a boil. Salt the water and cook the gnocchi in four to five batches until they rise to the surface, about 2 minutes. Using a slotted spoon, transfer the cooked gnocchi to the skillet with the sauce. When all of the gnocchi are cooked, place the pan over high heat for 1 to 2 minutes and toss the gnocchi with the sauce. Remove from the heat, add the remaining 1/4 cup Parmigiano, and toss again. Divide the gnocchi among serving plates and shave the white truffles, if using, over the top.