You can buy and cook kidneys from a variety of animals; lamb and pig kidneys tend to be the most tender, which makes them suitable for sautéing or grilling. Calf and ox kidneys are less tender and may require long, slow braising or simmering to ensure that they do not become tough and rubbery.

Before cooking any type of kidney, you will need to remove the fat and membrane surrounding the kidney and the gristly core at its centre.
Lamb's Kidneys
Lamb's kidneys are mild and delicious - perfect for grilling or frying.
Pig's Kidneys
Pig's kidneys are larger than lamb's kidneys and somewhat stronger in flavour. They are tender enough to be grilled or fried, but may also be chopped up and cooked slowly in stews and casseroles.
Calf's Kidneys
This multi-lobed kidney may be small and dark if taken from grass-fed veal, or large and pale if taken from milk-fed veal. Both types may either be slowly roasted in their own casing of fat for around an hour, or they may be briskly grilled or fried and served with a mustard and cream sauce.
Ox Kidneys
Ox kidneys are large (about 450 g in weight) and tough, making them suitable only for braising or slow-cooking. Their strong flavour provides richness for stews, pies and meat puddings.