Tiella barese (also tiella di riso, patate e cozze) is Bari's magnificent one-pot baked dish—layers of sliced potatoes, rice, mussels on the half-shell, tomatoes, onions, garlic, pecorino, and olive oil assembled in a wide terracotta or metal pan (the tiella) and baked until the rice absorbs the mussel liquor, the potatoes soften, and the top develops a golden, crisp crust. The dish is Bari's answer to Spanish paella—a complete meal in a single vessel where seafood, starch, and vegetables meld during slow baking. The assembly is architectural: a base layer of sliced potatoes, then raw rice (traditionally a short-grain variety), then opened mussels arranged shell-side up, scattered with sliced onion, halved cherry tomatoes, minced garlic, chopped parsley, and grated pecorino, then another layer of potatoes on top, the whole doused with olive oil and enough water to just cover the rice. The baking (180°C for about an hour) transforms the raw assembly: the mussels release their briny liquor into the rice, the potatoes on top crisp while those below turn creamy, and the rice cooks to a tender, flavour-saturated state somewhere between risotto and pilaf. The pecorino melts into pockets throughout. The dish is traditionally prepared for the feast of San Nicola (December 6th) in Bari, though it's eaten year-round. Every family in Bari claims the definitive recipe, and arguments about the correct layering order, whether to add zucchini, and how much water to use are perennial.
Layer: potatoes, rice, mussels (on half-shell), tomatoes, onion, garlic, parsley, pecorino. Top with potatoes. Drizzle generously with olive oil. Add water to just cover the rice. Bake at 180°C until rice is cooked and top is golden. Use raw rice—it cooks in the mussel liquor.
Soak the mussels overnight in salted water with a tablespoon of flour—they purge sand and plump up. The potatoes should be sliced about 3mm thick—too thin and they disintegrate, too thick and they don't cook through. A final blast at high heat (220°C for 10 minutes) crisps the top beautifully. Rest 10 minutes before serving so the rice firms up.
Pre-cooking the rice (it must cook in the dish, absorbing mussel liquor). Too much water (makes it soupy) or too little (rice stays hard). Removing mussels from shells (they should bake on the half-shell). Skipping the top potato layer (provides the essential crust).
Touring Club Italiano, Puglia in Cucina; Mary Taylor Simeti, Pomp and Sustenance