The French, renowned for their culinary excellence, pride themselves on being able to include every part of the cow in a tasty dish. Regrettably, this includes finding uses for the many internal organs, one of the more challenging of which are the kidneys. I have never eaten kidneys myself (nor do I plan to), but I imagine that they would not taste very good. They are, after all, the source of urine (not that I've drank that before, either, but it can't be tasty). The classic French dish for kidneys is "rognons de veau sauce moutarde" (veal kidneys in a mustard sauce).
Other cultures also have incorporated this nephrologic bent into their cuisine. The British, for instance, have their steak and kidney pie, which typically uses kidney from either lamb or pig The Swedish cook up a dish called Hokarpanna (a stew containing kidneys), while the Spanish
"Riñones al Jerez" attempts to mask the kidney taste with a sherry-based sauce.