Did you know that cod used to be a very highly prized, valuable trading commodity? Wars and battles were won on salt cod because, of course, in the old days ships were sailing for weeks or months and the sailors would have a very unhealthy diet. Having salt cod on board as a source of protein kept them going, and it meant they could jump off the boat with enough energy for a bit of fighting when it was required! All kinds of cultures began to salt fish – I suppose Iberian and Nordic countries are particularly well known for still doing it today. And certainly the Italians are more than partial to their fair share of it. Hundreds of years ago the only way to get fish into the centre of Italy would have been to use preserved fish like salt cod. It might sound obvious, but this is why Tuscan cooking is predominantly meat- and bean-based. In the old days the only common fish recipes would have used either preserved or fresh lake fish.
Unless you live in a country where it’s prevalent, like Portugal or Spain, salt cod can only be bought in good delis. Try to hunt out the real baccalà, but if you can’t find any then simply buy some fresh fish which can be salted overnight. As salt cod is preserved using copious amounts of salt, avoid seasoning this soup at all or do it right at the very end.
If using fresh cod, haddock or monkfish, pack it in a few handfuls of sea salt overnight and rinse it before using. If using proper salt cod, soak the fillets in cold water for 24 hours, changing the water a few times during this period. This way, the fish will rehydrate and the saltiness will be removed before cooking. If the fish is more than 2cm thick it might need up to 36 hours’ soaking.
Chop the onion, carrots, celery, garlic and parsley stalks. Heat a splash of olive oil in a saucepan, and add the chopped vegetables, parsley stalks and dried chilli. Sweat very slowly with the lid ajar for 15 to 20 minutes until soft, but not brown. Add the tomatoes and simmer for 10 minutes, then add the stock and bring back to the boil.
Break up any larger pieces of tomato with a wooden spoon and drop the salt cod fillets into the hot soup. Simmer gently for 15 minutes, just until the fish has poached and flakes apart when prodded with a fork. Pick out any bits of skin. Gently fold the flakes of fish through the soup, taste and season with pepper, salt (if needed) and a little lemon juice. Chop the parsley and celery leaves and scatter over the soup. Drizzle with plenty of extra virgin olive oil.