Prepare the honey mustard dressing first.
Prepare the watercress by just snapping off the woodier pieces of stem, then simply wash and dry. Now put a griddle, or frying pan if you haven’t got a griddle, over a medium to high heat and when almost, but not quite, blue smokey hot brush the steaks with oil, sprinkle a little salt over and put them oil side down on the griddle / in the pan.
Cook to your own satisfaction; Cook for around 4 minutes on each side for medium rare, depending how thick the steak is; around 3 minutes on each side will leave your steak rare and 5 minutes, well done. Don’t forget to oil and salt the other side of the steaks before you turn them. If the steaks are particularly thick, add a minute per side.
While the steak is cooking prepare the salad by adding the watercress and mushrooms to two bowls. When the steak is cooked, slice thinly, add to the bowls and toss. Finally sprinkle the dressing over lavishly and take to the table while the beef is still warm.