This is a favourite luncheon dish in France, one of those excellent petits plats, dainty and yet sufficing.
Remove the fat and skin from the kidneys, and cut in very thin slices. Melt the butter in a sauté pan and, when very hot, put in the sliced kidneys, the bayleaf, and season with salt and pepper. Cook for a few minutes on a brisk fire, shaking the pan, and turning the kidneys with a spoon. When nearly done—they should not take longer than 8 to 10 minutes in all—sprinkle with a little flour, stir it in well, then remove the pan from the fire, and add the white wine. Replace on the fire, and stir a few minutes longer. Serve very hot.