Gnocchi all’Ossolana are hearty cold-weather dumplings from the Ossola Valley in northern Piedmont, only a few miles from the Swiss border. In addition to the potatoes we know and love, these gnocchi are packed with winter squash and chestnut flour, which not only amplifies their warm flavor, but also gives them a rich, caramel color.
800 grams (1¾ pounds; about 1 small) butternut squash Extra-virgin olive oil 700 grams (1½ pounds; about 2 large) baking potatoes, scrubbed 120 grams all-purpose flour 120 grams chestnut flour 1½ teaspoons kosher salt 85 grams (3 ounces) finely grated Grana Padano or Parmigiano-Reggiano 2 egg yolks, lightly beaten Whole nutmeg
Heat the oven to 425°F/220°C
On a slip-free cutting board, cut the top and bottom ends off the squash, then cut it in half crosswise where the neck meets the base. Stand each piece upright on its widest flat side and carefully slice from top to bottom, making sure your free hand is holding the squash in place above the knife. Scoop out the seeds and coat the squash in olive oil and kosher salt.
Place the squash cut sides down on a parchment-lined sheet pan. Prick the potatoes all over with a fork and place them alongside the squash. Roast until the squash is browned and easily pierced with a knife, and the potatoes are tender with a crisp skin, 50 to 60 minutes, rotating the pan halfway through. If the potatoes don’t feel quite done, return them to the oven and bake, directly on the middle rack, for another 10 minutes.
When the potatoes are cool enough to handle, scoop out the flesh and pass it through a ricer or gently mash with a potato masher—you should have about 400 grams (14 ounces). Spread the potatoes on a paper towel–lined sheet pan and let cool for about 30 minutes. Pat dry with more paper towels before using.
When the squash is cool, scoop out the flesh and mash until smooth—you should have about 400 grams (14 ounces). Spread it on a paper towel–lined sheet pan and thoroughly pat dry to remove as much moisture as possible (use a few changes of paper towels to really sop it up!).
Combine the flours and salt in a large mixing bowl. Make the dough as directed for the Potato Gnocchi Dough. You do not need to rest the dough before shaping.