Marinated in soy sauce, sesame oil ... Michelle McGlinn uses this idea in the form of a grilled cheese sandwich, toasting beef bulgogi between melty gouda and a pile of shredded mild cheddar.
If possible, use soup soy sauce to season the broth ... I usually make my own marinade for the beef, but you can also buy bottled bulgogi marinade. The commercial marinade is saltier and sweeter ...