Choc-Pix Tasty Girls is belgian-white chocolate, with a molding of three naked girls.
But that's not the gimmick. When you shine some light on it at the right angle, the molding reveals the same image but in photographic form.
There is nothing added to the chocolate bar to make it do this. Rather, a very intricate texture is carved into the surface of the bar, so that light reflects off it in such a way to produce the photgraphic image.
£2.95 from Boys Stuff