Set on the poissoniere or fish-kettle half-full of water, put in an onion stuck with cloves, a bay leaf, salt, a handful of parsley and half cup vinegar. When it oils put in the fish on the moveable drainer bottom and boil gently about half an hour. Slide off the drainer on to a dish. Serve by cutting portions with a broad fish slice. Parsley sauce and new potatoes in the same plate.