Cut the Guanciale into 1 cm squares.
Place a large pot of water on the stove. Heat over medium heat until boiling. When the water boils, add a tablespoon of coarse salt (or according to the instructions on the pasta package). Wait a minute for the salt to dissolve, then add the spaghetti. Reduce the heat slightly so that the water boils but does not leave the pot. Stir the spaghetti from time to time during cooking to cook them evenly.
While you cook the spaghetti, heat a large non-stick skillet over medium heat. Place the Guanciale in the skillet. Cook the Guanciale, stirring occasionally with a wooden spoon, until it is soft and releases all the fat. Guanciale should not be fried too much, so as not to harden. This will take about 2 minutes, then turn off the heat.
With a slotted spoon, transfer the Guanciale to a bowl, leaving the fat in the pan.
While the spaghetti is cooking, prepare the egg cream. Mix egg yolks with Pecorino cheese and freshly ground black pepper. Slowly add 3 tablespoons of the cooking water to the eggs, stirring constantly to avoid the scrambled eggs effect. This procedure will keep you from getting the “scrambled egg effect” when mixing egg sauce with hot spaghetti.
Add 4–5 tablespoons of the pasta cooking water to the pan in which Guanciale was cooked. Prepare pasta “al dente” according to package instructions.
Drain spaghetti directly into the hot skillet. Sauté spaghetti with Guanciale fat for 1 minute over medium heat, stirring constantly. Add cooked Guanciale and sauté 1 minute more.
Turn off the heat. Wait 1 minute, then pour the egg cream over the spaghetti and stir. Now pay attention to the consistency. The perfect Carbonara should be creamy. If your carbonara is too sticky and dense, add 1-2 tablespoons of cooking water and mix well. If it is too runny, you can add some grated pecorino cheese.
Your authentic pasta carbonara is ready! Divide among 4 plates and sprinkle with more Pecorino cheese and ground black pepper. Serve immediately!