The heat of the water cooks them slowly to a jelly-like consistency, leaving the yolk harder than the white. If liked, rich lard as for frying before you put in the second water, stir in a very little water, the second time. When they are tender, add for each sweetbread a heaping teaspoonful of butter, a little chopped parsley, pepper, salt and little cream. Let them simmer in this gravy for five minutes. Send to the table in a covered dish with gravy poured over them.
Sweetbreads are the thymus glands of veal, young beef, lamb and pork.
These glands are connected by a tube, which is often removed before sweetbreads are marketed. Sweetbreads from milk-fed veal or young calves are considered the best. They're very perishable and should be prepared within 24 hours of purchase. Before being cooked, sweetbreads must be soaked in several changes of water with vinegar, lemon or lime juice added and their outer membrane removed. Some recipes call for the glands to be blanched to firm them, and refrigerated until ready for use.