Lamb’s Kidneys with Mustard Sauce

Kidneys oozing blood are a little too rare for the British taste, but veal or lambs’ kidneys should only be rapidly but lightly cooked, brown outside and a rosy pink within. Cook them too long and they will be tough and dry. The exception to this rule is ox kidney, which is the preferred one for use with steak in a pie or pudding, when long slow cooking is needed to produce a succulent texture.