This cream of mushroom soup is SO comforting and delicious! Veggies like mushrooms, cauliflower, celery, and leeks create its rich flavor and creamy texture, so this recipe is both vegan and gluten-free.
Heat the oil in a large pot or Dutch oven over medium heat. Add the leeks, celery, and ¼ teaspoon salt and cook 5 minutes, stirring occasionally. Add the mushrooms and cook until soft, 8 to 10 minutes more.
Stir in the tamari, wine, garlic, and thyme and cook for 30 seconds to 1 minute, or until the wine has evaporated. Add the broth and the cauliflower.
Simmer uncovered for 20 minutes, or until the cauliflower is very soft. Transfer to a blender, add the mustard and vinegar, and blend until smooth. If your soup is too thick, add a little bit of water to the blender to reach a creamy consistency. Season to taste and serve with desired toppings.