We make vegetarian onion soup that GF (who's a meat-eater) likes even better than the real stuff made with beef broth. We just do veggie broth/bullion, white wine, and onions in the crock pot. I'm only lacto-ovo, not vegan, so we do the gruyere cheese on top. But maybe you could do soy cheese on top?
You wouldn't think that veggie broth and onions could be so good, but we love it. GF calls it "liquid gold."