Ingredients
For the Pasta:
Kosher salt
6 ounces baby spinach, trimmed (about 8 cups)
2 1/2 cups all-purpose flour, plus more for dusting
3 large eggs
1/4 cup freshly grated parmigiano-reggiano cheese
Semolina flour, for dusting
For the Sauce:
2 tablespoons extra-virgin olive oil
4 ounces guanciale (cured pork jowls), cut into thin matchsticks or strips
1 large Spanish onion, chopped
3 large egg yolks, beaten
2 cups freshly grated parmigiano-reggiano cheese, plus more for garnish
Very thinly shaved fresh white truffle, for garnish
Preparation
Make the pasta: Bring 3 qts water to a boil large pot and add 1 T salt. Set up an ice bath next to the stove. Blanch the spinach in the boiling water, about 2 min, then remove with tongs and plunge into the ice bath to cool. Drain the spinach and squeeze dry. Set aside.
Combine the flour and spinach in a food processor and process until evenly green. With the motor running, add the eggs and cheese and process until the dough forms a ball around the blade. Continue to process until smooth, about 20 more seconds.
Dust a large board with flour; turn the dough out onto the board and knead a few times by hand. The dough should be elastic. Wrap in plastic wrap and let rest about 30 min at room temp.
Cut the dough into 4 pieces. Cover 3 in with a slightly damp towel. Flour the board; roll out 1 piece of dough with a floured rolling pin into a 10"by14" rectangle, about 1/8" thick. Brush dough lightly with flour, then roll up and cut into 1/2" wide strips using a sharp knife. Place the pasta in nests on a sheet tray that has been dusted with semolina flour. Cover with a clean dish towel and set aside at room temp. Repeat with the remaining pieces of dough.
Bring a large pot of salted water to a boil. Make the sauce: Heat the olive oil in an extra-large skillet over med heat. Scatter in the guanciale and cook until the fat is rendered and the guanciale is crisp in spots, about 3 min. Remove the guanciale and drain on paper towels; remove all but about 1/4 C drippings from the skillet. Add the onion and cook until soft, 10 to 12 min. Return the guanciale to the skillet.
