Cooking beef for pepper steak From American-"Chinese" restaurants, I usually order a dish called "Pepper Steak with Onions". This seems to be a simple enough dish, mostly a straightforward stir-fry, except for one unique characteristic: the beef comes out soft and easy to chew, much like chicken. 

How is this achieved? Is it a certain cut of meat? A certain cooking technique?
Meat in stir-fries is often velveted. That makes for a supremely soft chunk of meat, and it can be done with any type of meat. This answer actually addresses chicken: How to cook extremely soft chicken?, but it applies just as well to beef. It's usually done with egg and cornstarch, but sometimes it's done with a small amount baking soda instead, as in this recipe for Beef and Broccoli.