Soak the salt cod in cold water for 24 hours, changing the water at least three times. Heat water in a deep pan, wash and cut the leeks into large pieces (including the green leaves) and cook in the water for one hour with the bay leaf. Season with salt. Half way through the cooking process, add the potatoes and the cod broken into pieces and the Spanish olive oil. Remove the bay leaf when the dish is cooked. Porrusalda can also be made without cod.