Kidneys are one of the flagship products of French and English gastronomy.
Fact sheet
Rognons is the culinary term for an animal's kidneys, which belong to the "red" tripe group. Their quality stems in particular from the age of the animal and the way they are cooked.
Taken from the animal's fifth quarter, they come in different shapes and sizes (lobed for beef and veal, similar to a large dried pulse for mutton) and were formerly considered a "commoner's" dish in Balzac's time.
This tripe product must be eaten very fresh. Their freshness can be confirmed by their colour and firmness, and a cover of fat only enhances their quality. Butchers sell them prepared and washed. When preparing beef kidneys, it is advised to rinse them in boiling water and vinegar before cooking them.
Veal kidneys are tender enough to be cooked using dry heat, by grilling or sautéing them. Don't overcook them, though, or they'll quickly become very tough. Before cooking them, peel off the outer membrane. Due to their mild flavor, they don't need to be soaked.
Beef and mutton kidneys can be eaten with a range of sauces, grilled, pan-fried, made into brochettes or casseroled. Beef kidneys are often used to enhance stews. As with tripe products in general, they should be cooked with care and attention. Lamb's kidneys are best for grilling but they must be separated first. Restaurants often serve this dish with a potato puree.
