The stockfish should be cooked in an earthenware casserole dish. Slice the onion and sauté it in a cup of oil.
As soon as it begins to brown, add two or three green chilies, a few basil leaves and a little chopped parsley, salt, pepper and 500 g of peeled and pureed tomatoes plus salt. Let the tomatoes cook well and then add the chopped stockfish, still adding a generous glass of oil.
Then add black olives and pine nuts to taste, plus a few capers. Lower the heat and cook gently, diluting with a little hot water at a time when needed.
When the stockfish is cooked, sprinkle with grated Parmesan cheese.