Pecorino e fave is a sandwich that exists for about six weeks a year, and the broad bean is the reason. This is the spring ritual of central Italy: when the first tender fave come in, raw and sweet and barely podded, they are eaten with young sheep's-milk cheese, and the panino is the portable form of that custom. The defining ingredient is not the pecorino, which is deliberately the mildest young one, but the raw fava itself, podded by hand and eaten green, grassy, and faintly bitter at the skin. The whole thing is built around catching the bean at the moment it is good, which is why it appears and vanishes with the season and why nobody bothers with it the rest of the year.
The craft is keeping both halves raw and fresh and letting them stay separate textures. The fave are shelled at the last moment and used whole or barely crushed, never cooked, so the snap and the green sweetness survive; cook them and the sandwich loses its entire point. The cheese is a young, soft, mild pecorino, cut thick but kept gentle so it cushions the bean rather than fighting it, the salt of the curd answering the grassy bitterness of the skin. The bread is plain and often the unsalted Tuscan loaf, present to bind a loose, rolling filling that would otherwise scatter. A few drops of oil and a turn of pepper are the only additions; the balance is already in the pairing itself.
The variations are mostly about what the bean is allowed beside it. There is the version eaten with no bread at all, beans and cheese alone as the spring snack the panino is descended from, and the build that adds a slice of young salame to the fava and curd. Each is the same raw-bean-and-mild-cheese moment with one thing changed, and each deserves its own article rather than being crowded in here.