La Fraternal

I truly love La Fraternal. It is a such a cosy place, the staff is friendly and engaged, and it embodies the vegan way of life beyond "making food": they also offer a nice range of vegan products, as well as yoga courses, alternative workshops on cooking/yoga/health etc., alternative life-style-magazines, music events, ...
The daily menu has been brilliant every time I have been there, starting with the delicious home-made bread and daily dip-creation, followed by a creative, daily fresh and healthy main course (two options available), and a surprising dessert. The composition on the plates is always beautiful and creative. The fresh juices and lemonades are highly recommendable too. The kitchen-team is inventive, this is not your "can-do-this-at-home-as-well"-food, this is (working-with-your)soul-food.

Definitely high up there on the list of places to try in Santiago if you're after some inspiring food. They were quite happy to veganize our menu del día without making it boring.
If the location (i.e. not near a Metro) puts you off, hop on the 104 bus at Los Leones (Suecia con Providencia) and get off when it crosses Simon Bolívar. From there it's a 2 min walk.

I visit this restaurant regularily and I'm very satisfied with their service and variety. The food is very healthy and tasty. Nice atmosphere and fast service.