One of the most flavorful of all steak dishes and one of the most inexpensive if you carve it right: across the grain, paper-thin, with the knife almost parallel to the cutting board. So while you start with a piece of meat that’s only about one inch thick, each slice is about 2 inches wide. (That’s where the economy comes in; a little looks like a lot.) There’s absolutely no waste, either.
Score the surface of the steak on both sides. Combine all the other ingredients for a marinade. Place the meat in a flat utility dish and pour the marinade over it. Cover and refrigerate for 12 hours, turning occasionally. Remove from the marinade.
Preheat broiler. Broil steak 2 to 3 inches below heat, about 5 minutes on each side. A flank should be cooked rare or it will toughen. Serve with the classic Bearnaise Sauce.
Combine the wine, vinegar, onion, pepper, tarragon and chervil in top of double boiler. Cook over direct heat until reduced by half. Strain the mixture. Allow to cool.
Beating briskly over hot water, add alternately, a little at a time, the egg yolks and melted butter. When finished the sauce will have the consistency of Hollandaise Sauce.