Rice, potatoes and mussels is a typical Puglian dish. It is found in the Bari area and in the province of Taranto; the two versions are known locally as ‘Tiella Barese’ and ‘Tiella Tarantina’. The name derives from the ‘tiella’ pot traditionally used to prepare the dish: a wide, low clay baking dish in which rich and succulent dinners were prepared for the peasant workers. Because people were often very hungry, the ingredients were poor and there was little time available, the peasants used to use anything to hand: vegetables, rice, potatoes and mussels (the most economical and available seafood). It was cooked over the embers, a metal cover was placed over the top and more coals were placed on top, thus simulating baking in the oven. The result was uniformly excellent, just as yours will be when you make this dish!
Clean the mussels of their beards, scrub them well, then leave them to soak in fresh water for half an hour, changing the water a couple of times. Meanwhile, soak the rice in cold water: this will remove any excess starch. Do the same for the potatoes, having peeled and cut into not-to-thin slices. Peel and slice the onions and tomatoes. Then prepare garlic and parsley, chopped finely together. Drain the mussels and put them on the heat in a saucepan with the lid on, adding nothing else: after five minutes they will be open. Remove half the shell from each of the mussels. Lightly grease a baking dish. Make a layer of potatoes, of onions, of tomatoes, then sprinkle with the chopped garlic and parsley, salt, pepper and a frizzle of extra virgin olive oil. Arrange all the mussel shells with the meat facing up. If there are any mussels left, remove the shells completely and distribute evenly. Cover with the rice, filling all the spaces and the shells. Add a little salt: soon we will add the cooking liquid from the mussels which is already quite salty. Then complete with the remaining ingredients, onion, tomatoes and potatoes. Finish with a generous sprinkling of cheese, which you could also add to the internal layers of your dish if you like. Now strain the cooking liquid from the mussels and add water or vegetable broth until you get 500 ml. Pour into the baking dish, and bake at 200 °C for 40 minutes + 15 minutes to rest. Serve.