They use a tenderizing powder like papain or bromelain or something similar that i am not aware of. Sure velveting will give it a silky texture but its not going to make the inside of the meat very very soft. My guess is there is a technique to using these tenderizing powders, because ive tried using them and they do work, but always left a noticeable taste.
I want to point out before someone suggests quickly cooking hot and fast producing very soft meat, sure. But, have you ever had leftovers and reheated them in the microware? I have, ive even nuked them to the moon and back and guess what? Still very very soft meat! Whats up with that?
