The kidney is an organ of slaughtered animals, which belongs to the family of red offal; the largest and also more consistent one is that of beef, which has a reddish brown color, while that of veal is more tender and slightly lighter. Bovine kidneys have the surface divided into many "lobes". On the other hand those of sheeps, pigs and goats have a bean shape, a smooth surface and a light brown-red color.
Before consuming it, the kidney should always be left to drain in water and vinegar for at least half an hour so that it loses its characteristic smell. The bovine one (normally the calf one is used) must also be deprived of the large white, fat and spongy knot, which forms an agglomeration right in the center of the kidney. It should be cooked briefly, otherwise it hardens. The kidney is good stir-fried, grilled or on skewers.