Korean supermarkets are one of the best-kept secrets for a quick lunch; nearly every one has at least one lunch counter, and some--like the H-Mart in Garden Grove's Korean District--have entire food courts.
The H-Mart at Diamond Jamboree, though, is suffering: there's a Korean bakery with the usual assortment of soft, milk-dough pastries and breads, and there used to be a Pizza and Chicken Love Letter until it closed; now, the only thing left is a lunch counter that used to be called Bibigo. In one of those trademark wars that makes perfect sense to attorneys and confuses the hell out of customers, it changes names and is currently back to its original name of Sobahn Express.
Sobahn Express is one of the few "express" places to deserve the name; they specialize in bibimbap, rice with vegetables and a fried egg cooked in a burning hot stone pot called a dol sot. Once you tell them what kind of meat (if any) you want, they throw your ingredients in the dol sot, put a couple of dishes of panchan and a bowl of soup on the tray, and call your name. Two minutes from the time you put your wallet away to the time you're eating--and Koreans eat their food burning hot.
The bibimbap is actually not bad, especially for the speed with which it's put together. Bean sprouts, spinach, pickled daikon, cucumbers, your meat, and a sunny-side-up egg atop rice which quickly develops an appealing brown crust on the bottom where it meets the cast iron pot. If anything, the food is underseasoned, unusually for Korean food; that's where the dispensers of gochujang--spicy bean paste--come in. The gochujang isn't especially spicy, so load it on there.
For a quick lunch, it beats any of the other places in Diamond Jamboree, which take a lot longer to get food to the table; at under $7, it's a good bargain, too. Honestly, the thing that takes the longest is winding your way through that parking lot, which appears to have been designed by a crayon-wielding third-grader; it can take as long to park as to buy and eat lunch. Tip: park in the parking structure behind the H-Mart, and enter from McGaw instead of from Alton.