The panino con salame cotto is built around the one salame in the Piedmontese repertoire that is cooked rather than air-dried. The mixture of seasoned pork is cased like any salame, but instead of being hung to lose moisture over weeks it is gently cooked through, which leaves it soft, pale, mildly spiced, and faintly steamy in character rather than firm and concentrated. This is the defining fact: it is closer in texture to a cooked sausage or a mild cooked ham than to the snapping coin of a dry salame, and the sandwich is shaped around that softness, not against it.
The craft is in cutting and carrying a meat that has no dry structure. Salame cotto is sliced thick, because thin slices have nothing to hold them and tear into shreds; cut in generous rounds it stays tender and slightly springy against the bread. It is often eaten just-warm, the way it is sold at the Piedmontese counter, when the cooked fat is at its softest and its gentle pepper-and-garlic note is most open. The bread is plain and structured, a crusted roll, so the give of the meat meets a crust with some resistance rather than collapsing into a soft crumb. Almost nothing else is added, because the cooked salame is already a complete, rounded thing; the panino is a frame for it, decided at the salumeria counter where it was cut rather than at assembly.
The variations are best read against the rest of the salame family, and each is its own subject. The soft jar-preserved salam d'la duja of Piedmont, the firm hand-tied Felino of Parma, the large-grained sweet Varzi of the Oltrepò, the garlic-driven mantovano, the fennel-cured Sicilian Sant'Angelo: each is a separate salame with its own cure and bread, and the cooked, warm cotto stands apart from all of the air-dried ones. Each of those deserves its own article rather than being crowded in here.