Soak the fish in an earthenware or enamelled dish for at least 24 hours, changing the water at least twice. Then poach it in fresh water.
Flake the fish, removing the skin, and pound it to a cream with the oil and garlic. Cook the potatoes and mash them to a purée, then beat them into the fish together with the three egg yolks and the seasonings. Mix very well. Whisk the egg whites and