Cut the fish across into two or three pieces, put these in water in an earthenware pot, skin side up, and soak for 24 hours. Change the water once or twice.
Cook the pieces offish in an earthenware vessel with plenty of water, starting from cold, with 1 or 2 bayleaves. Do not let the water boil, as boiling would toughen the fish. Once it is steaming, simmer for 5 minutes, then take the pot off the fire and leave to stand for half an hour. Drain, remove the grey skin and the bones, and flake the fish.
Peel the potatoes and onion, and slice them to the thickness of a coin. Put some olive oil in the bottom of pan (the sole pan is good for this), put in a layer of potatoes and onion, then a layer of flaked fish, and repeat. Sprinkle with origano and black pepper, barely cover with milk, and simmer until the potatoes are cooked; by this time a good deal of milk will have been absorbed or will have evaporated, and what remains will have acquired a creamy consistency. Add a little grated nutmeg and a few drops of oil from the chilli (see peperoncini sott ’olio) at this point, and some finely chopped garlic and parsley at the end of the cooking. Sliced hard-boiled eggs and black olives, unstoned, can be added. (Stoned olives stain the pale cream colour of the dish.)