1Cook the spaghetti al dente according to the package instructions.
2Toast the black peppercorns in a dry frying pan for a few minutes.
3Crush the peppercorns coarsely with a mortar and pestle.
4Remove the skin from the guanciale and cut the rest into small cubes.
5Place the guanciale in a cold pan, gradually increase the heat, and slowly render the fat until crispy. Do not add to a hot pan immediately to avoid burning.
6Reserve the rendered fat and the crispy guanciale separately.
7Finely grate both cheeses.
8Place the egg yolks in a bowl.
9Mix the egg yolks and grated cheeses until smooth.
10Stir in the crushed black pepper and some of the guanciale fat into the cheese-egg mixture.
11Combine the cooked spaghetti and half of the crispy guanciale in a pan and mix well.
12Turn off the heat, add the carbonara sauce, and mix. Add just enough pasta water to create a creamy sauce.
13Serve the spaghetti carbonara on a plate, sprinkle with the remaining guanciale and extra Parmesan cheese.