These places serve meatless all-vegie healthy food but still got the absolutely top notch flavor.
"SanChon" in Insa-dong area.
"JoGum" also in Insa-dong area.
and my all time fav. "Chaegundaam" in Datch-dong area.
(although the web didn't help me much...)
http://www.chaegundaam.com/
This... is a bit hard one...
no web, no English sign or menu, and hardly seen non-Koreans there either.
Even the direction is not very easy. But if you ask any locals, most of them know where.
"Jinjoo Hwegwan(?)" near Seoul City Hall.
I miss this place.