How to Make It
Preheat the oven to 350°F. Line a rimmed baking sheet with parchment paper or foil.
Scrub the sweet potatoes, prick them in a few spots with a fork, and set them on the prepared baking sheet. Bake until the sweet potatoes are completely tender throughout, about 1 hour. Let cool.
When the sweet potatoes are cool enough to handle, split them open and scoop out the flesh. Press the flesh through a potato ricer or food mill into a large bowl, or finely mash it with a fork. You should end up with about 2 cups of mashed sweet potatoes.
To the sweet potato, add the egg, pecorino, salt, pepper, and nutmeg, and mix well with a fork. Add the 1½ cups flour and use the fork to work it in, setting aside the fork once the flour is just incorporated. Use your hands to fold and press the dough into a ball. Put the ball on a lightly floured work surface and knead the dough just until it is uniform and slightly springy, about ten times.
Dust a rimmed baking sheet with flour. Divide the dough into 4 equal-size pieces. Dust the work surface with some fresh flour, and roll each piece of dough into a rope with a ½-inch diameter. Cut the ropes at ½-inch intervals with a knife or bench scraper (you can make them bigger or smaller to suit your taste; adjust cooking time accordingly). Dust them with a bit more flour, so they aren’t sticky to the touch.
If you like, working with one at a time, use your thumb to roll each dumpling over the tines of a fork or a gnocchi paddle and onto the floured baking sheet. (The grooves and dimples that form on the surface of the gnocchi will help catch the sauce that dresses them.) Refrigerate until ready to cook. (Alternatively, freeze them on the baking sheet, making sure the gnocchi are not touching, until firm. Pop them off of the baking sheet and store in a plastic zip-top bag in the freezer for up to 1 month.)
Bring a large pot of water to a boil and salt it. Add two handfuls of gnocchi at a time, cooking them until they float and more than half of each gnocchi is bobbing above the surface of the water, about 3 minutes for fresh gnocchi and 4 to 5 minutes for frozen. Using a spider, transfer them to a waiting skillet or bowl and repeat with remaining gnocchi
TIPS : Seek out the drier and slightly starchier white-fleshed sweet potato varieties for making gnocchi.
A fork is key to mixing and shaping the dough; a bench scraper is also a great tool for dividing the dough and lifting the tender, shaped dumplings.
Sweet Potatoes: Roasted, Loaded, Fried, and Made Into Pie