5 oz Boccalone Guianciale
1 medium onion, finely chopped
1/4 cup dry white wine
1 lb spaghetti
5 large egg yolks
1 1/2 oz Parmigiano-Reggiano, finely grated (3/4 cup)
3/4 oz Pecorino Romano, finely grated (1/3 cup)
1 teaspoon coarsely ground black pepper
1/4 teaspoon salt
Bring a large pot of salted water to a boil for cooking spaghetti.
Cut Boccalone Guanciale into 1/3-inch dice. Heat a deep, heavy-bottomed 12-inch skillet over moderate heat. Cook the Guanciale, stirring, until fat begins to render, about 1 to 2 minutes. Add the onion and cook, stirring occasionally, until onion is golden, about 10 minutes. Add the wine and boil until reduced by half, 1 to 2 minutes. Turn off heat.
Cook spaghetti in the pot of boiling, salted water until al dente.
While the pasta is cooking, whisk together the egg yolks, grated cheeses, salt and pepper in a small bowl.
Drain spaghetti in a colander and add to Guanciale-onion mixture. Turn heat to mediu-low and toss pasta with tongs until coated. Remove from heat and add egg mixture, tossing to combine. Serve immediately.