This panuozzo is defined by the way a baked pizza dough treats two filling elements that behave very differently under heat: a raw prosciutto that must not cook, and a fresh mozzarella that is supposed to. The carrier is the Gragnano pizza-dough roll, baked plain, split, filled, and returned to the oven. On that second pass the mozzarella melts and strings through the warm crumb while the prosciutto crudo is laid in only after, or right at the end, so its fat softens and its scent lifts without the cure being cooked away. The pairing needs both states: the cheese is the hot, milky bind that glues the sandwich; the raw ham is the cool, salty, fragrant note dropped on top of it. Cook the ham and you lose its perfume; leave the cheese cold and the panuozzo is just bread.
The craft is in the order of assembly and the timing of the heat. The dough is baked first so the crust sets and the inside steams hollow, then split while still pliable. The mozzarella is torn rather than sliced and drained well, because a wet cheese floods the crumb on the return bake, and it goes in for the hot pass so it slackens into the bread rather than sitting as a cold lump. The prosciutto is the last thing in, laid in loose folds over the just-melted cheese so the residual heat relaxes its fat and releases its scent without stiffening it. The second bake is short and fierce, enough to string the cheese and re-crisp the shell, no longer. A good build comes out with cheese pulling between the halves and the ham still tender and aromatic on top; a poor one bakes the prosciutto grey and dry, or serves the cheese unmelted.
The variations stay within the Gragnano-dough family and each deserves its own article rather than being crowded in here. There is the plain panuozzo with nothing but the baked dough, the version with salsiccia and bitter friarielli instead of ham and cheese, and the builds that swap the fresh mozzarella for a smoked provola that strings differently and adds a wood note. Each is a distinct balance struck against the same double-baked bread.