If possible we prefer to eat vegetarian, so we went out of our way to find vegetarian or vegan restaurants on our trip. This is how we found out about Buddhist cuisine which follows some pretty strict rules. I think basically they are not supposed to eat things that have to be fully killed in order to be eaten. This rules out animals and certain vegetables like onions which you have to pull out to eat. I could be wrong on this though! Anyway!
We found Sanchon, which serves a 20-or-so course meal of this kind of temple cooking. It is considered to be one of the best vegetarian restaurants certainly in Seoul, some even claiming in Asia, and has been featured in the news and online (I recommend visiting the latter link for its photos and descriptions of dishes). We got there fairly early in the evening, they had just opened, and so we had the restaurant to ourselves for some time. Most courses are tiny dishes of this or that vegetable. Most were absolutely delicious, but a few just tasted and felt like bitting into freshly mown lawn. The food was good and the atmosphere was absolutely dreamy, so I would recommend going there if you’re ever in the area.