Kidneys are part of the innards . The main ingredients for dishes - mostly ragouts or soups - are mainly kidneys from lamb , veal and pork , and less often from poultry .
Beef kidneys are seldom cooked whole, they are too firm and are only used in pieces for blood and liver sausage . The fat surrounding the kidneys is usually processed into kidney fat , especially beef kidney fat .
For preparation, the kidneys are first freed of their fat capsule and skinned and the urinary tract is removed. Then they are watered. In order to flush out the urine as much as possible, multiple rinsing is recommended. Another method is to soak the kidneys in milk. Depending on the recipe, the prepared kidneys are cut into slices or cubes and briefly steamed , braised or fried . If they cook for too long, they will become hard. Like livers , kidneys should only be salted towards the end. If a sauce is made from the roast set , the kidneys should be removed beforehand and only briefly warmed up in them at the end, otherwise the taste of the sauce will suffer.
Sour kidneys are a traditional southern German and Rhenish-Westphalian dish . The well-known Zürcher Geschnetzelte is also refined in the classic method of preparation with shredded kidneys (Nierli). Kidneys can also be prepared as soup .