The panuozzo is defined by its bread above all, because the bread is pizza. It is a length of Gragnano pizza dough, the same lean, well-fermented dough used for a Neapolitan pizza, shaped into an oblong, baked plain in the wood oven until it puffs and blisters, then split and filled and returned to the oven to warm through. The defining fact is that the carrier is not a roll but a baked dough that stays light and chewy with a thin, crackling crust, built to take a hot filling and a second pass through the heat. Plain, before anything goes in it, it is already the point: an airy, faintly charred pizza bread the size of a forearm. Treat it as ordinary sandwich bread and the form is lost; the oven is half the recipe.
The craft is in the dough and the double bake. The dough is fermented long and slow so it bakes light rather than dense, then cooked first on its own so the crust sets and the inside steams hollow, which is what lets it be split cleanly without tearing. The split is done while the loaf is still warm and pliable, and the filling is laid so it will heat evenly when the panuozzo goes back in: nothing so wet it makes the crumb soggy on the return pass, nothing so dry it scorches. The second bake is short and hot, just long enough to warm the filling, slacken any cheese, and re-crisp the crust without drying the bread to a board. A good panuozzo comes out with a shell that shatters slightly and an interior that is still soft and a little chewy; a sloppy one is either pale and bready or baked twice into a rusk.
The variations are mostly the fillings carried in this same baked dough, and the classics deserve their own articles rather than being crowded in here. There is the panuozzo with prosciutto and mozzarella, the one with salsiccia and bitter friarielli, and the plainer builds with a single cured meat or a melting cheese alone. The Gragnano carrier stays constant; what changes is what it is asked to hold, and each of those pairings is a distinct balance worth its own piece.