In a bowl, whisk the egg yolks with two-thirds of the grated Pecorino and a little black pepper until a smooth, creamy mixture forms.

Cut the guanciale into slices about 2 mm thick and place them in a large pan over medium heat. Cook until the fat renders and the pieces become lightly crisp.

Cook the spaghetti in salted boiling water until al dente, then drain, reserving a little of the cooking water.

Add the drained spaghetti to the pan with the guanciale and toss well so the pasta absorbs the flavor.

Turn off the heat and add the egg mixture along with a little of the reserved pasta water. Stir quickly for about 30 seconds, just enough to create a creamy sauce without scrambling the eggs.

Finish by sprinkling with the remaining one-third of the grated Pecorino and serve this traditional Italian carbonara immediately.