Roll out the pasta dough to the thinnest setting on a pasta machine
. Cut the dough crosswise into 1/4-inch strips. Place the tagliatelle on a sheet tray that has been dusted with semolina
flour, cover with a clean dish towel, and set aside until ready to use.
Bring 6 quarts of water to a boil and add 2 tablespoons of salt.
In a 12 to 14-inch saute pan, cook the pancetta
over high heat until it is browned and the fat has been rendered, about 10 minutes. Add the butter and parsnips and saute over high heat without shaking the pan too much until they are golden brown and slightly crispy, 5 to 6 minutes. Season, to taste, with salt and pepper, add the parsley, and cook 1 minute longer.
Cook the tagliatelle in the boiling water until tender yet al dente
, about 2 minutes. Drain
the pasta, reserving some of the cooking water, and add the pasta to the pan with the pancetta and the parsnips. Toss over high heat to coat the pasta, adding pasta cooking water if necessary to keep the sauce
form getting too tight. Divide equally among 4 heated pasta bowls, grate
Parmigiano-Reggiano over the top of each bowl, and serve immediately.