If you are looking for Vegan food in Seoul, you might want to consider Plant.
I've blogged about it previously here and they have since extended their place to 2 outlets- Plant Bakery and Plant Cafe & Kitchen which are situated nearby.
We ordered the fame avocado burger and sesame peanut soba bowl to share and this new place has more natural light and room compared to the previous store now bakery.
So yes, it's definitely a place to go for a vegan meal and hopefully i'll be able to hop over for some of their cakes and share with you not a bite but some visuals of it soon.^^
