I must confess that this dish came together because what I had left in the refrigerator when we wanted to have veal kidney. There was still half a cooked cauliflower waiting for use.
The rognons are popular in France. In the Netherlands, most people would not think about eating it. In England, the kidneys of the adult cows enter in the steak and kidney pie.
The first time I ate kidney it was as a kind of test by my then new boss in France in a restaurant. There I was served a whole kidney with some mustard sauce and I not only passed the test but also started to like it.
Cut-up kidney is easier for frying, what I did with the following dish.