Tiella di Riso Patate e Cozze Barese

Place the scrubbed, debearded mussels in cold salted water and soak for 30 minutes to expel any sand. Drain and discard any that are open and do not close when tapped. Hold each mussel at its hinge and work a short knife between the two shells to prise it open, leaving the mussel seated in one half-shell and the raw internal liquor retained within. The mussel is ready when it is opened raw, sitting in its half-shell, its sea water undisturbed.

Heat the oven to 200 °C. Rub the base of a terracotta tiella generously with olive oil. Arrange the potato slices in a single, overlapping layer to cover the base completely. Season the layer lightly and scatter over a third of the garlic and parsley. The base is ready when every part of the dish's floor is covered — no gaps through which rice could fall and scorch.

Scatter half the Arborio rice in an even layer over the potatoes. Add the oregano. Nestle the opened mussels, shell-side down, across the rice so that their retained liquor will drain directly into the rice below. Scatter the remaining garlic and most of the remaining parsley over the mussels, then cover with the remaining rice. Pour the 300 ml of water evenly across the surface — this, combined with the mussel liquor released during baking, is the only liquid the rice will receive. Do not add more. The layer is ready when the mussels are fully embedded and the water has been poured to the measured quantity — no more, no less — because it is here, and only here, that the dish lives or dies: too much water and the rice will never crisp; pre-steamed mussels and there is no sea water to give.

Lay the zucchini slices across the rice in an even layer, then arrange the tomato slices over them. Scatter the grated Pecorino across the entire surface without restraint — the cheese must cover fully so that it caramelises into a continuous golden crust. Drizzle olive oil over the top. Cover the dish tightly with foil or a lid and place in the preheated oven for 30 minutes. The dish is ready for uncovering when the kitchen carries the scent of steaming mussels and cooked potato rising from the sealed vessel.

Remove the cover and return the tiella to the oven for a further 15 minutes. The dish is done when the Pecorino surface is deep gold and carries caramelised patches, the tomato edges are blistered, and a knife inserted at the side meets the resistance of cooked — not raw — potato at the base.

Remove from the oven and rest, uncovered, for 5 minutes. Scatter the reserved parsley. Serve directly from the terracotta dish. The preparation is ready when the layers hold their form under a large spoon and each portion shows distinct strata: golden crust, collapsed zucchini and tomato, rice studded with mussels, and an intact potato base.