Parboil and blanch them. When cold, cut into neat dice, add a tablespoonful of chopped mushrooms for each sweetbread ; put them all together in a saucepan, cover with white stock, or with butter and water, pepper and salt, and heat to a boil. Strain off the gravy, and return to the saucepan, heaping sweetbreads and mushrooms upon a dish and keeping them hot. Thicken the gravy with a white roux; stir in a great spoonful of cream and pour over the dice. You may omit the mushrooms if you choose.