Bari and the Taranto coast, Puglia — tiella barese is the emblem of Bari's cucina. The preparation reflects the Adriatic mussel aquaculture tradition of the Taranto lagoon (the Mar Piccolo), which has produced mussels since ancient Greek times. The terracotta tiella is the essential vessel — it gives the dish its name.
Riso, patate e cozze (or tiella barese — named for the terracotta tiella dish) is the defining baked preparation of Bari and the northern Puglia coast: alternating layers of raw Arborio rice, thinly sliced raw potato, and fresh mussels (cozze Tarantine, the mussels of the Taranto lagoon) in their half-shell, seasoned with abundant Pecorino, tomato, onion, parsley, and olive oil, then baked covered until the rice has absorbed all the mussel liquor and the potato beneath has cooked and taken on the mussel's brininess. It is cooked and served in the same terracotta tiella. The preparation requires fresh live mussels — their liquor is what cooks the rice. No other liquid is added.
Riso, patate e cozze from the tiella is a preparation of extraordinary unity — the rice has absorbed the mussel liquor and taken on a briny sweetness; the potato beneath is soft and infused; each mussel in its half-shell sits in its own pocket of seasoned rice. The Pecorino and olive oil tie everything together. To eat it in Bari with a glass of Primitivo is to understand the entire southern Italian kitchen in a single dish.
Scrub and beard mussels; open by hand (or briefly heat in a dry pan — but only until they open, immediately remove). Keep one shell; remove the other. Reserve all mussel liquor. In the oiled tiella: layer sliced potato (seasoned with salt, olive oil, and grated Pecorino); lay mussels in their half-shell in a single layer; cover with uncooked Arborio rice (seasoned with olive oil, diced tomato, chopped onion, parsley, Pecorino, salt, and the strained mussel liquor); repeat layering if tiella is deep enough. The mussel liquor must be sufficient to cook the rice — add a little water if the mussels were not very liquor-rich. Drizzle olive oil over top. Cover tightly with foil; bake at 200°C for 40-45 minutes. Uncover for last 10 minutes to colour the top.
The tiella (shallow terracotta baking dish) distributes heat perfectly for this preparation; a thick baking dish or a cast-iron skillet are the best substitutes. Tarantine mussels (from the Taranto lagoon — an enclosed brackish-saltwater lagoon with exceptional mussel flavour) are the historical reference; any fresh, live, high-quality mussels will work. The Pecorino grated between layers is the Barese marker — Parmigiano is not traditional here.
Not reserving the mussel liquor — the liquor is the cooking liquid for the rice; without it, the dish is bland and the rice won't cook properly. Using overcooked mussels — mussels should be just opened; any further cooking before baking makes them rubbery. Arborio rice not raw — the rice must go in raw to absorb the mussel liquor during baking.
Anna Gosetti della Salda, Le Ricette Regionali Italiane; Slow Food Editore, Puglia in Cucina