This used to call for a cheap cut of flank steak but flank steak has been 'discovered'. It's not worth $6-7 a pound. It is probably my fault, I spent years singing the glories of the stuff and people finally believed me. That is the way of it all. If you can find it use soy sauce made with water, soy beans, and salt and nothing else. It is much richer and better. Portions and cooking time are a guess.