Hyesung Noodle House
One of Seoul's best-established purveyors of kalguksu, knife-cut noodles. The OG one literally only does kalguksu, the new Los Angeles branch adds in buchimgae (vegetable pancake) and bossam (pork belly) for a menu that's three times the size.
The buchimgae is a bit too much green onion and not enough batter/dough, we skipped the bossam (Kobawoo is almost certainly better), and the kalguksu, as good* as it is, is hard to get excited enough about to make it worth a special trip.
* = don't get me wrong, it's very good.