Here's the wiki article on the subject. I say that merits a try!
Flat iron steak is the American name for the cut known as
Butlers' steak in the UK and
oyster blade steak in Australia and New Zealand. This cut of
steak is from the
shoulder of a beef animal[
citation needed]. The steak encompasses the
teres minor and
infraspinatus muscles of beef, and one may see this displayed in some butcher shops and meat markets as a "top blade" roast. Steaks that are cross cut from this muscle are called
top blade steaks or patio steaks. As a whole cut of meat, it usually weighs around 2 to 3 lbs, is located adjacent to the heart of the shoulder clod, under the seven or paddle bone, which is analogous to the shoulder blade in a human. The entire top blade usually yields 4 steaks, between 8 to 12oz. each. Flat iron steaks usually have a significant amount of
marbling. Anatomically, the muscle forms the dorsal part of the rotator cuff of the steer. This cut is anatomically distinct from the
shoulder tender which lies directly below it and which is analogous to the
teres major in a human.
Raw Flat Iron steak
Restaurants, particularly upscale, have recently begun serving flat iron steaks on their menus. Especially popular are flat irons from
Wagyu beef, as a way for chefs to offer more affordable and profitable dishes featuring
Wagyu or
Kobe beef. To make it more marketable, the steak, which has the fascia separating the infraspinatus and teres minor within it, has, in recent years, been cut as two flatter steaks, each corresponding to one muscle, with the tough fascia removed.
In the North American Meat Processor (NAMP) meat buyers guide, it is item #1114D Beef Shoulder, Top Blade Steak. The NAMP lists it as the second most tender cut, after the Tenderloin, and followed (in order) by the Top Sirloin Center-Cut, the Ribeye and Strip Steak Center-Cut, and finally Beef Shoulder, Arm.