This panuozzo is the Neapolitan sausage-and-bitter-greens pairing carried in a baked pizza dough, and what defines it is bitterness held against fat inside a bread that goes back into the oven. Friarielli are the leafy tops and buds of a local broccoli relative, wilted hard in oil with garlic and chilli until they collapse into a dark, faintly mineral, bitter tangle. Set against a coarse pork salsiccia, the greens are the equal half, not a garnish: the sausage brings rendered fat and salt, the friarielli bring a green bitterness that cuts straight through it. The Gragnano dough is the third actor, baked plain then split and filled and returned to the heat, so the fat and the bitter oil bleed into a warm, chewy crumb rather than a cold roll. Take the greens out and it is a sausage bread; skip the second bake and it is the same filling in lesser bread.
The craft is in cooking both fillings until they meet in the middle and timing the return bake. The sausage is grilled or pan-cooked so its fat renders and its casing colours, then split lengthwise so the cut faces caramelise and the meat lies flat in the dough. The friarielli are cooked down properly rather than warmed, because underdone they read harsh and stalky, and the garlic-and-chilli oil they carry is what dresses the inside of the bread. They go into the split loaf hot, layered so the sausage fat and the bitter oil run together, and the panuozzo goes back into a hot oven briefly, long enough to marry the two and re-crisp the shell without drying the crumb. A good build comes out with the bread chewy and oil-stained and the bitterness still sharp; a sloppy one is either greasy and slack or baked twice to a rusk.
The variations stay in Campania and around this same dough, and each deserves its own article rather than being crowded in here. There is the salsiccia and friarielli served in a plain roll rather than the baked panuozzo, the version with provola laid over the sausage so the cheese strings into the greens, and the friarielli carried alone in the dough for the meatless table. Each pulls the pairing somewhere distinct enough to stand on its own.