Even if you use salt cod that’s already been desalted, leave it to soak in cold water for at least a morning and change the water a couple of times; if you buy it still salted, leave the fish to soak for 2 days, changing the water 4 times a day. Use a sharp knife to remove the skin from the cod and then cut it into square pieces measuring roughly 4 cm. Clean and wash the onion, celery, carrot and parsley, then chop them finely together with the chilli pepper and sauté with the olive oil in a large, heavy-bottomed pan. When the vegetables have turned golden brown, put the pieces of salt cod into the pan, stir and sauté. Now add the peeled tomatoes chopped into pieces and the finely chopped cloves of garlic, season with salt and pepper, stir and leave to cook for about 10 minutes, then turn off the heat. Clean the spinach, wash it under running water and, still dripping wet, transfer it into a saucepan; put the lid on and cook for a few minutes, stirring from time to time, until it softens. Strain off the water when the spinach it’s still “al dente” (the leaves mustn’t fall apart), wait 5 minutes for it to cool a bit and then squeeze it well, forming small balls. Chop the spinach finely, add it to the pan with the cod and toss over a low heat for a few minutes. Taste and season with salt if necessary, then turn off the heat and leave to rest for 10 minutes. Serve the cod with slices of toasted bread. 

The expression “in zimino” indicates a tasty way of cooking cuttlefish or salt cod – as well as pulses, in particular chickpeas – with chard or spinach. It’s typically used in Tuscan and Ligurian cuisine.