Freeze beef for about 15 minutes to firm a little, making it easier to slice. Slice thin against the grain.
In a bowl, coat beef pieces well with cornstarch to tenderized. Let the beef sit in the cornstarch for about 15 minutes. Rinse cornstarch from beef and return beef to bowl.
Add marinade to beef. Let the beef sit in the marinade for about 15 minutes.
Heat wok or large skillet with oil. Remove beef strips from marinade in batches to brown meat in oil. Transfer meat to a plate until all is cooked. Reserve both cooked beef and marinade.
If needed, add a little additional oil to the wok or pan. Add garlic and ginger and cook on medium heat until fragrant, about 3 to 5 minutes. Add reserved beef and marinade to the pan and continue cooking until the beef is well done.
Add green onions and cook until just starting to wilt, about 5 minutes. Serve over rice.
