Tarallo farcito is defined by a bread that was never meant to be soft, split and asked to hold a filling anyway. The Puglian tarallo is a small ring of hard dough, often boiled then baked the way a bagel is, made firm and durable and scented with fennel seed, black pepper, or white wine in the dough itself. Filled, the larger ring or tarallone is sliced through its waist into two stiff arcs that clamp around something soft. The defining tension is structural: the ring is dry, crunchy, and assertively seasoned, so the filling has to be moist and fatty enough to soften the inner crumb just slightly and to answer the fennel and pepper already baked in. A bland wet filling would have nothing to say to the spiced shell, and a dry one would leave the whole thing rattling and hard to eat. The two are built to compensate for each other.
The craft is in the split and in choosing a filling that does the bread's missing job. A good tarallo for filling is the thicker tarallone, sturdy enough to survive being cut in half without crumbling, and it is split cleanly so the two arcs sit flush. The classic fillings are soft and Puglian: creamy burrata or stracciatella, a fresh primo sale, marinated vegetables under oil, or a folded slice of capocollo or local salame. Whatever goes in must carry fat and moisture, because the ring brings none and the dough's own pepper and fennel need a soft, rich counterweight rather than competition. Good practice fills it just before eating so the crunch survives to the first bites and softens only where the filling touches. A sloppy version uses a thin brittle snacking tarallo that shatters on the cut, or a dry lean filling that leaves a hard, seasoned ring with nothing to bind it.
The variations stay in Puglia and the wider south, swapping the soft centre while keeping the ring. There is the tarallo filled with burrata and a few oil-cured tomatoes, the one with marinated mushrooms or grilled aubergine, the one folded around capocollo di Martina Franca, and the sweet glazed tarallo that is a different animal entirely, eaten as a biscuit rather than split. There is also the smaller plain tarallo served not filled but alongside cheese and wine, the same dough without the sandwich logic. Each is its own spiced-ring-and-soft-centre pairing, and each deserves its own article rather than being crowded in here.