The vegan mozzarella cheese sauce and homemade croutons that top this French onion soup create a trifecta of flavor. It's as good as you want it to be. It's a bit labor intensive. And worth it. You can skip the homemade croutons if you have good bread.
As this recipe has a lot of ingredients and takes a lot of time, consider doubling it. Delicious leftovers are so convenient, and you can freeze it. The cheese sauce can be used in another meal (or eaten solo) . . .