I made this over the weekend. I usually marinade the meat for a few days, but this time I boil it over medium heat until the sauce is almost dry. I was pretty sure DH liked it the last time I made some. However, this time, he not very fond of it, I used pork when he liked it. I think the beef has a stronger flavor for tocino marinade. I'll make sure to marinate it for a few days next time. ODS enjoyed it with hot steamy rice.
I also pound the beef to make it tender. But I noticed that it did not make a difference. As soon as it started cooking it all harden and the simmer process made it tender again.
Or maybe I should have keep on pounding until it was really tender? All I can do is try again, and make it better next time.