When you buy fish and have it filleted, ask for the bones and trimmings to be sent also. Put a quart of milk to heat and add to it a bunch of mixed herbs, a few minced shallots, parsley, pepper and salt. Throw in your fish and cook for an hour. If you have any celery put in a piece, or two or three white artichokes. Strain the soup, taste it, and add more salt or more milk as you think necessary. Return to the pan. Take the yolk of an egg and just before taking the soup from the fire, stir it quickly in. This soup must never boil. It should be made out of the very white fish, excluding herring and mackerel.