The trapizzino con pollo alla cacciatora carries a hunter's chicken braise into the pocket, and the bread exists to make a bony stew portable. The shell is the usual trapizzino: a triangle of pizza-bianca dough baked until the crust crackles and the crumb stays open and springy, slit along the long edge and held upright to take a spoonful of something wet. Pollo alla cacciatora in the Roman manner is chicken on the bone browned in oil, then stewed with onion or garlic, rosemary, white wine or vinegar, tomato, and sometimes anchovy and olives until the meat is falling off and the sauce has thickened with the chicken's own collagen. For the pocket the bird is pulled off the bone entirely, so what goes in is shredded dark and white meat in a clinging savoury sugo, and the bread is the only structure the dish now has.
The craft is in the boning and the reduction. A good cacciatora for this use is cooked until the meat surrenders, then stripped completely of bone, skin, and cartilage so nothing in the pocket fights the eater; the sauce is reduced past a forkable stew until it is glossy and tight, because a thin tomato-wine braise runs straight through a trapizzino crumb. The shell is baked hard at the cut faces so the sugo sits on the surface rather than soaking in, and the filling goes in hot, pushed to the closed corner of the triangle so the open top stays dry in the hand. A little of the rosemary chopped fresh over the top, or a few of the braised olives, keeps the filling from flattening into a single tomato note. The sloppy build leaves bone shards in, under-reduces the sauce, and overfills the pocket until the bread fails.
The close cousins all start from a pan of browned chicken and each deserves its own article rather than being crowded in here. There is pollo alla cacciatora served on the bone as its own plate with bread alongside, the white cacciatora in bianco that drops the tomato for wine and herbs and eats sharper and lighter, and the trapizzino con polpette al sugo which solves the same tomato-braise problem with ground meat instead of pulled bird. Each is a different argument about poultry and sugo, and each is its own subject.