Steps

To make classic carbonara, first cut the guanciale into 1/4-inch layers, then into long, 2-inch strips.
Combine the egg yolks with the grated cheeses and a pinch of black pepper. If desired, add 2 tbsp milk for a creamier sauce.
Heat 1 tbsp oil in a frying pan and brown the strips of guanciale for 2 minutes until crisp, then turn off the heat and leave to cool.
Cook the pasta in plenty of salted water; set aside a ladleful of the pasta water, then drain the pasta once it is cooked al dente.
Pour the reserved hot water into the part of the frying pan containing the cooled guanciale: this will prevent the pasta from drying out.
Transfer the pasta to the same pan and mix together,|then add the yolk and cheese mixture, stirring rapidly. In the warm pan with the hot pasta, the eggs will cook gently and become creamy. It is important to do this part quickly to prevent the yolks from congealing and taking on the texture of scrambled eggs.
Season with freshly-milled black pepper and serve immediately on heated plates.