Slice onions in half from root to tip, remove the skins, then thinly slice from root to tip and add to a large Dutch oven.
Add ¼ cup of water and sauté on medium heat for 30-45 minutes, stirring often and adding water as needed.
Cut the baguette into ¾" slices and toast in a toaster or a 350°F oven until browned.
Prepare the broth by bringing 5 cups of water to a boil, adding dried mushrooms and veggie base, stirring well, then removing from heat.
Once rehydrated, remove the mushrooms, dice them, and add back to the broth.
Stir minced garlic into the onions once they’ve browned.
Deglaze the pan with sherry, scraping up any browned bits from the bottom.
Add the broth, thyme bundle, and soy sauce; simmer for another 15-20 minutes. Ladle into crocks, top with toasted baguette and vegan cheese, then broil until melted. Serve hot.