Jackpot!
I had seen this hamburger shop by chance on seollal, and it was closed. Some weeks later, a texan friend said this was one of his favorite places for hamburgers in Seoul, so my bf and I headed there again to try.
The hamburgers were amazing. The patty tastes like real meat, fresh, (I think they make the patties there), and really really juicy. I got the most simple one, just with grilled onions, cheese, and home sauce... it was amazingly good. The fries were also very good.
Decoration is nice, american diner style, and the 3 workers there (2 guys and a girl at the cashier) are young, energetic and nice. The restaurant is small and we arrived at 11:30, a bit later it got full, but the service is fast so rotation is fast as well.
Totally recommend it, and will go back to also try the shakes.