The kidneys of food animals and birds, eaten as edible offal. Rich in protein, iron, and B vitamins, they are prepared by soaking and careful cooking to mellow their strong flavour — steak-and-kidney pie being the classic showcase. As organs that filter blood, they can accumulate certain residues and heavy metals, so sourcing from inspected animals and observing any consumption guidance matters. Trimming and soaking reduce both flavour intensity and surface contaminants. Quick, hot cooking keeps them tender rather than rubbery.