The panino con ricotta salata is the dried, salted opposite of the fresh ricotta sandwich, and the contrast is the entire point. Ricotta salata is sheep's-milk ricotta that has been salted, pressed, and aged until it is firm enough to slice or grate: chalk-white, dense, dry, and pointedly salty, with a clean lactic tang and a crumbly break. It behaves nothing like the spoonable fresh curd; it is a seasoning cheese, the same thing grated over pasta alla Norma in Sicily, and on a sandwich its job is sharp salt and structure rather than creaminess. The build is decided by that firmness: this cheese is shaved or sliced and stands up on the bite, where fresh ricotta would be spread and yield.
The craft is using a salty, dry cheese without making the sandwich too aggressive. It is cut into thin slices or shaved into curls so its salt distributes through every bite instead of landing in one hard wedge, and because it does not melt it stays a textural element, a firm contrast against softer things around it. The bread is plain and soft so it cushions the dryness, and the cheese is balanced by something with moisture or sweetness rather than more salt: ripe tomato and oil, a few grilled vegetables, sometimes a fruit note or fresh greens to answer the cure. Restraint matters here in the other direction, since ricotta salata is loud and a little goes a long way; the discipline is to let one well-aged, salty cheese season the whole sandwich without overdoing the quantity.
The variations follow that salt-and-balance logic, each its own preparation rather than a footnote here: the Sicilian build with tomato and oil; the grilled-vegetable version where the cheese seasons the lot; and the shaved-over-greens reading where it acts as a finishing salt. Each is the same dried-salted-ricotta logic given a loaf, and each deserves its own article rather than being crowded in here.