The panino con cotoletta milanese is built around a specific cut, and that is what separates it from the generic breaded-cutlet panino. The Milanese cotoletta in its strict form is a veal chop with the bone left in, crumbed and fried in butter, thicker through the middle than the pounded slab most cutlet sandwiches use. That thickness changes the whole sandwich. A thin cutlet is all coating and a sliver of meat; the bone-in Milanese gives a deep, juicy core under the crust, which means the bread has to manage a wetter, heavier filling while still protecting a crisp shell.
The craft is reconciling a moist interior with a coating that must not go soft. The chop is fried in butter so the crumb takes on a richer colour and flavour than an oil fry gives, and it is cooked to keep the centre tender, which leaves more internal steam to fight on the way to the hand. The meat is usually cut off the bone for the panino so it sits flat, but it stays noticeably thicker than a milanese pounded for a plate. The bread is plain and sturdy enough to take the weight without crushing the crust, often briefly toasted inside so it does not add to the moisture load. Salt is light because the crumb is already seasoned, and the dressing stays minimal, a little lemon or nothing, since the butter-fried crust is the loud element and a sauce would only soften it. It is eaten hot, while the contrast of dense meat and brittle coating is still sharp.
The variations stay close to the cut: the version with peppery rocket cutting the butter, the one with a shaving of Grana, the lighter boneless reading that drifts back toward the generic cutlet panino. Each of those is a distinct balance on the same thick fried chop, and each deserves its own article rather than being crowded in here.