A panino with pecorino sardo is really two different sandwiches depending on one word on the label: dolce or maturo. The Sardinian sheep's-milk cheese is a protected denomination made in both, and they are not interchangeable. The dolce is young, pale, soft, and mild, faintly milky and sweet, the kind of cheese sliced thick like a table cheese and eaten in quantity. The maturo is aged hard, granular, sharp, and pointed, closer to a grating cheese than a sandwich one, used thin and used sparingly. The defining decision is made before the bread is touched: choosing which pecorino sardo you are building around determines how much goes in, how it is cut, and what, if anything, is allowed to join it.
The craft follows from that fork. The dolce is sliced into generous, supple sheets that fold into a plain roll and carry the sandwich largely on their own, the bread doing little more than holding a soft, mild cheese that does not need much rounding. The maturo is shaved or broken into thin, brittle pieces and used in a fraction of the quantity, because at that age and salinity a thick layer would overwhelm the bread the way the hard romano does. A Sardinian build typically meets the cheese with the island's own larder: a smear of bitter miele di corbezzolo, the strawberry-tree honey, against the aged version, or nothing at all beside the young one. The bread is plain and the additions few, scaled to whichever cheese is leading.
The variations are the island's own pairings rather than reinventions of the format. The dolce turns up against fresh broad beans in spring and the maturo against that bitter honey or a few drops of oil, and there is the leaner build where the cheese stands alone with bread and nothing else. Each is the same Sardinian wheel met by one Sardinian thing, and each deserves its own article rather than being crowded in here.