Fry the onion and garlic in olive oil until golden, add the wine and reduce down by two-thirds. Add the tomato coulis and parsley, thyme and chilli. Season with salt and freshly ground black pepper.
Roll up the mackerel fillets and skewer with a cocktail stick. Put the mackerel rolls in the tomato sauce, add the peas and cook gently for about 10 minutes. Remove the cocktail sticks.
Serve in shallow soup bowls with bruschetta seasoned with extra-virgin olive oil, crushed garlic and a couple of turns of sea salt from the salt mill.
Fresh-water eel can be cooked in the same way, in this case cut the eel into cutlets.