To prepare kidneys for cooking, begin by removing any outer fat or membranes.
Cut the kidneys in half lengthwise and remove the tough white gristle from the inside.
Once this is done, rinse in cold water and, to reduce some of the stronger flavor of the kidney, soak in cold water with a pinch of salt and 1 Tbsp. of apple cider vinegar (or the juice of 1 lemon) for 1 hour.
Drain, pat dry with paper towel, and proceed with the recipe as written.
This information is an excerpt from It Takes Guts by Ashleigh Vanhoute and can be purchased here.