Salt Cod Cooked in Olive Oil and Sherry Vinegar

• 1½ lb / 680 g thick fillet of salt cod
• 1 lb / 455

Soak the salt cod for at least 24 hours and up to 48 hours in several changes of cold water. Drain, put it in a shallow saucepan and cover with fresh cold water. Over a low heat, bring the water just to the point where the surface breaks.

Remove from the heat, and put to one side. The fish will continue to cook without toughening. Meanwhile, scrub and boil the potatoes until tend