Organ meats like beef kidneys aren't popular in the United States, though French chef and cookbook author Jacques Pepin says that kidneys can be a tender and flavorful cut if prepared correctly. Unlike lamb or veal kidneys, beef kidneys are large and tough and require long braising over low, moist heat to become soft. Add chopped vegetables to the braising liquid along with the kidneys to make a stew that can be spooned over rice or mashed potatoes, or serve cooked beef kidneys with crusty whole-wheat bread to mop up the sauce. Eat beef kidneys only occasionally since they are high in cholesterol.
Make a cut in the thin membrane surrounding the kidneys using a sharp knife. Remove and discard the membrane.
Slice the kidneys in half, lengthwise. Cut out and discard the round lump of white fat in the center of each kidney half.
Rinse the beef kidneys thoroughly under cool, running water. Pat the meat dry with paper towels. Cut each beef kidney half into 1 1/2-inch chunks.
Fill a large bowl with cold water. Add a small amount of plain vinegar or lemon juice and a pinch of salt. Put the beef kidney pieces into the water and allow them to soak for two hours.
Drain the kidney chunks in a colander, discarding all of the soaking water and the liquid that comes out of the meat.
Pour water and your choice of wine into a large saucepan. Plan on 1 cup of wine and about 1 3/4 cups water for every 3 to 3 1/2 pounds of raw beef kidneys. Bring the liquid to a boil.
Stir the kidneys into the liquid along with chopped vegetables such as mushrooms or potatoes, if desired, and seasonings like garlic or thyme. Allow the mixture to boil, then reduce the heat to low.
Put the pan's lid in place. Continue to cook on low, stirring only occasionally, until the beef kidneys and vegetables are tender, about 45 minutes.