Throw spaghetti in boiling salted water and cook pasta al-dente. Save some hot water for the sauce.
*Guanciale is an Italian cured meat product prepared from pork jowl or cheeks. Bacon is often used as a substitute. Beat the egg, yolks and add grated cheese gradually, hot pasta water and ground black pepper. Meanwhile, in a hot pan cook pancetta until browned and crisp with a drizzle of olive oil (optional). Remove some of extra fat using paper towels. Save half of the pancetta for garnishing. Turn heat back on pan where pancetta is been sitting. Stir in cooked pasta with pancetta and add a splash of pasta water; turn heat off. To prevent eggs from scrambling, transfer pasta into a large bowl and add sauce.
Arrange a nice swirl of spaghetti on warm plates. Garnish with the remaining pancetta, add parmesan shavings and freshly ground pepper. Serve immediately, buon appetito!