Prepare all the ingredients and put the water on high heat. Salt it when it's warm.
Start cooking the guanciale in a pan. First, at low heat, to let the fat melt, then at medium heat, to make it crispy (but not fried).
Separate the yolks and whip them with a fork.
Add the grated pecorino cheese and keep on whipping until you obtain a nice cream.
In the meanwhile, guanciale should be ready.
Remove some cooking water from the pot where the pasta is almost done.
A minute before the pasta is done, remove it from the water and pour it in the pan over the cooked guanciale. Mix it in the melted fat.
Add the egg and pecorino cheese cream.
Add some spoons of the cooking water and mix the pasta.
Serve it, add some more pecorino cheese and (according to taste) some black pepper. Buon appetito!