As a Korean from Seoul, Here's my recommended restaurant :
Bong-Hee Seolong-Tang , famours for its Selong-Tang (soup bolied with beef, beef-bones etc). Even Kim Young Sam (a former president who screwed the korean economy during Asian Financial Crisis period
) went to this place to have this soup. I personally tried and loved it. It should be fine with westerners.
Enpyong-Gu, Sinsa-Dong 35-25 (North-west of Seoul)
If you get off at "Sa-Jeol" station of Subway Line no.7, you are right next to this place. Just ask people around where this place is and they will surely know.
I will further advise on good restaurants in Seoul area.
p.s : By the way, the best western meal I've ever had in Seoul was in US army base
