Salt Codfish Lyonnese Style

Put two pounds of codfish to soak for eighteen hours after paring well the surface; change the water every six hours, then place the fish in a saucepanful of cold water, bring to boiling point and set it on one side of the range to let bubble only without boiling for half an hour, then drain it off. Mince finely half a pound of white onions; fry them slowly in four ounces of butter and half a gill of olive oil on a very slack fire so that the onions cook while acquiring a golden color; add to it the well drained and shredded fish removing all the bones and skin, toss the whole for ten minutes over a brisk fire, adding at the last moment a pinch of pepper, and a crushed and chopped clove of garlic, also a spoonful of mustard and a dash of vinegar. Dress and surround with boiled potatoes cut in slices and fried in butter.