Why does Roman carbonara use pecorino instead of parmigiano?

Traditional Roman carbonara is made with pecorino romano, a sharp, salty sheep’s-milk cheese, not the cow’s-milk parmigiano reggiano most foreigners expect. Pecorino romano is one of Italy’s oldest cheeses and holds a Protected Designation of Origin (PDO) status, meaning it can only be made in Lazio, Sardinia, and a small part of Tuscany. Roman cooks insist on pecorino in carbonara, cacio e pepe, and amatriciana; using parmigiano marks a tourist or a Northern Italian. The flavor is sharper, saltier, and stands up to the egg-yolk-and-guanciale sauce in a way parmigiano can’t.

In this clip, an American cook in Rome confirms the choice: “Parmigiano or pecorino? Of course, pecorino. I knew that.”