The michetta con prosciutto cotto leads on the cooked ham. The constant under every michetta sandwich is the bread: the hollow, crisp-shelled Milanese roll, star-pleated and baked up almost empty inside so its thin shell shatters and it is filled light rather than packed. The variable here is prosciutto cotto, the pale, gentle, brine-cooked ham, laid into that hollow. This is the plain Milanese lunch in its most ordinary and most exact form: one mild ham, the local roll, and the discipline to add nothing that would mask either. The whole sandwich rides on a quiet meat and a noisy crust.
The craft is the slice against the shell. Prosciutto cotto is sliced thin and folded in loosely so it stays tender and lets air through rather than reading as a dense block that would crush the roll. The michetta's near-empty centre takes the folds without the shell being forced apart, so the bread keeps its shape and shatters on the first bite. Because the ham is delicate, the temptation is to add something with more volume, and the Milanese answer is to resist it: at most a thin film of butter where it bridges a very lean ham to the crust, never a sauce that would damp the shell or shout over a mild meat. The restraint is the recipe.
The named turns are the rest of the michetta cluster led from their own fillings: the roll around the fried cotoletta, around soft mortadella, around fine salame Milano, each a louder or richer filling than this quiet one. Each of those is the same hollow shattering roll built around a different filling, and each deserves its own article rather than being crowded in here.