Put on some water to boil. Take your lettuce, and choose the round kind, and wash it well. Take out neatly with your fingers the center leaves, and fill up instead with a sheep's kidney which you have lightly dusted with flour, pepper, and salt. Tie the lettuce round very firmly and set it in a pan of boiling water that covers up only three quarters of the vegetable. Boil for eighteen minutes. Take out the lettuce, untie it, drain it, and serve at once. Kidneys are good when they are placed inside large Spanish onions and gently stewed, in which case a dab of made mustard is given them.