Prepare as for roasting, but instead of larding lay them upon thin slices of salt pork, and strew about them a carrot, an onion, and a stalk of celery, cut into dice. Add a cupful of hot water or weak stock; cover closely and cook half an hour. Uncover, baste well with butter, then with their own gravy, and brown. Strain and rub the gravy through a sieve ; thicken with browned flour; boil up and pour over the sweetbreads.