Cut the seasoned “guanciale”/bacon (the barb, “Barbazza”) into thin strips and fry in a pan along with some sage leaves.
At the end of cooking (a few minutes) sprinkle with white wine vinegar, raise the flame and let it evaporate quickly.

Grandmother Pierina advises:
The “guanciale” must be crispy. Before adding the vinegar, drain the excess fat produced during cooking.