Pecorino di Norcia arrives in a panino carrying the place it comes from, and that place is a norcineria town. Norcia, in the mountains of Umbria, is so identified with curing and butchery that the word norcino means a pork butcher across much of Italy, and its sheep's-milk cheese is shaped by the same mountain economy: firm, savoury, made from the milk of flocks grazed on high pasture, often aged in cool stone. What defines the sandwich is the company the cheese keeps. This is not the table cheese of a gentle region but the dairy half of a larder whose other half is prosciutto and salame, and the panino tends to be built the way that town builds everything, around something cured and concentrated.
The craft is matching a firm mountain cheese to that context. The pecorino di Norcia is cut into sturdy slices or broken into pieces depending on its age, savoury and a little sharp from the pasture and the cellar, substantial enough to hold its own next to a strong cured thing rather than be lost beside it. The bread is plain and crusted, the same blank, sturdy roll the town's salume gets, present to carry weight rather than add it. The defining local move is the truffle: Norcia sits in black-truffle country, and a shaving or a smear of truffle paste against the sheep's milk is the regional flourish, used in the smallest measure because a little is loud. Cheese, plain bread, and one mountain accent, nothing crowded.
The variations are Umbrian and stay near the norcineria. There is the truffled build, the version paired with the town's own prosciutto, and the plain one where the firm cheese stands alone on bread. Each is the same mountain wheel met by one thing the town already makes, and each deserves its own article rather than being crowded in here.