Place as many kidneys as are required for a dish in boiling water for a few minutes, then remove the skin, cut them in two and take out the core. Wipe them, flour them lightly and fry them quickly in a small quantity of hot dripping for six minutes; then put aside while the sauce is made. Add sufficient clarified dripping to that in which the kidneys were cooked to make up one and a half ounces and fry one ounce of chopped onion in it until it is a light brown; then stir in one ounce of flour and one ounce of cornflour, and pour in gradually, stirring all the time, one pint of stock (or water); when the sauce is smooth and thick, season it with salt, pepper, and a little nutmeg, and add one dessertspoonful of tomato sauce, one teaspoonful of Harvey sauce, and sufficient browning to make it a rich brown. Strain the sauce into a gourmet boila (or a stewpan will do), put the kidneys into it and place the vessel containing them in a stewpan of boiling water, cover the pan and let them cook (preferably in the oven) for two hours, taking care to replenish the water when necessary. Dish up the kidneys inside a wall of mashed potatoes, and pour the sauce over them.