Combine one tablespoon of the soy sauce and one tablespoon of the sherry in a resealable storage bag. Add sliced meat and allow to marinate for 30min.
While the meat is marinating, combine the sauce ingredients which includes the remaining soy sauce and sherry plus the corn starch, brown sugar, sesame oil, ginger, garlic, green onions, beef broth, and fish/oyster sauce. Set aside.
In large skillet, heat oil on high heat. Drain off any marinade from meat. Just before the oil starts to smoke, add the meat to the skillet in a single layer. Cook just a minute or two on each side. Transfer to a large plate or bowl.
Reduce heat to medium and add broccoli. Cover and allow to steam for a couple minutes. You want the broccoli to be bright green and crisp tender. Do not over cook as it will continue cooking later in the sauce. Transfer broccoli to the plate with the meat.
Add the sauce to the skillet. Allow to cook and thicken for several minutes while scraping the bottom of the pan to release anything that might have stuck. Once the sauce begins to boil and thicken, add the meat, broccoli, and any juices that may have developed on the plate back to the skillet with the sauce. Toss to coat.
Serve with cooked short grain rice and top with additional green onions and sesame seeds, if desired.