re: London Broil

Hey Karen, here is how Cook's Ilustrated describes it:

There are a number of different cuts of beef sold as London broil in the supermarket. Which is the real or best one?

Truth be told, London broil is not a cut of meat, but a recipe in which a steak is grilled, broiled, or pan-seared and then sliced thinly on a bias across the grain. Traditionally, flank steak is the cut used for London broil, though these days you'll also find shoulder steak and top round steak sold as London broil cuts. Of these three, flank is the most expensive, and the most flavorful, but shoulder steak also makes a good London broil.