Prepare the carbonara cream. Add pecorino, parmigiano, a little water, and rendered guanciale fat to the egg yolks, then pasteurize in a water bath (bagnomaria), heating to 67-68°C. It keeps for 2 days refrigerated and gives the same result every time.
Egg yolks to tastePecorino Romano to tasteParmigiano Reggiano to tasteWater to tasteRendered guanciale fat to taste