Beef kidney is stronger tasting and tougher than veal or lamb kidney.
Butchers trim off the blood vessels, the pizzle cord, and the ureter before sale. Each beef kidney after this trimming will weigh about a pound (450g.)
Beef kidney needs slow cooking to tenderize it, either braising on its own or chopped up and put into a stew, or in the classic meat sauce for Steak and Kidney Pie.
Trim off the outer membrane, if the butcher hasn’t already. Then, cut the kidney in half lengthwise. I the centre, you will see a white piece of fat — extract and discard this,
Soak for an hour before using in something acidic, such as buttermilk or water with some vinegar or lemon juice in it. This will help to make the taste a bit milder, by leeching uric acid out of it.