We had a waitress once who didn’t believe that a fish could be called John. She stood at the pass thinking that we were winding her up and said, ‘You don’t get a fish called John!’ She didn’t last long. In France it’s called St. Pierre. The legend has it that the dark spots on the fish’s side are St. Peter’s thumbprints. You can substitute the black trumpet mushrooms for other wild varieties, but the trumpets add a fantastic earthiness to the dish and perfectly complement the salsify.