1Cut the guanciale into strips and crumble the butifarra.
2In a frying pan, add the guanciale, then the butifarra; cook until golden brown and set aside.
3In the same pan, add the previously chopped onion and cook for 20 minutes.
4Add the crushed tomato, mix well, and simmer for about 10 minutes.
5Add the guanciale and butifarra back to the sofrito and mix well.
6Boil the pasta until al dente.
7Meanwhile, in a large bowl, whisk the egg yolks with the grated parmesan cheese until smooth; set aside.
8Drain the pasta, reserving a little of the cooking water; add the pasta to the pan with the sauce and mix well to absorb the flavors.
9Remove the pan from the heat and add the yolk and parmesan mixture.
10Mix quickly so that the yolks do not curdle and the sauce remains creamy. If necessary, add a little of the pasta cooking water to adjust the consistency.
11Last step, plate and add more parmesan cheese on top and enjoy.