Beef, veal and pig’s kidneys should be plump, firm, and encased in a shiny membrane. When buying kidneys encased in fat, it should be off-white (see box). Avoid kidneys with a strong odour.
Trim away any fat and connective tissue, then pull off the outer membrane with your fingers.
Cut the kidney in half lengthwise, slicing through the fatty core. Hold the core with your fingertips and cut it away with a boning knife.
Thread the prepared kidney halves on to a skewer to keep them flat. They are now ready for grilling or pan-frying.