This is a slow-cooked onion soup with a broiled vegan cheese toast on top — the kind of thing that makes skeptical dinner guests ask for the recipe before they’ve finished the bowl. The whole process takes about an hour and a half, most of which is hands-off. It’s worth every minute.
The short version of why this works
Two things carry this soup: properly caramelized onions and layered umami. The onions need 45 minutes to a full hour over medium-low heat — not high heat with a splash of water to speed things up. Rushing that step gives you soft, pale onions instead of the deep, jammy, almost-sweet base that makes the broth taste like it simmered all day. The second piece is tamari plus balsamic vinegar. Together they replace the savory depth that beef stock and aged cheese normally provide. Neither ingredient announces itself; they just make the broth taste complete rather than thin.
Substitutions that actually work
- Tamari vs. soy sauce: Either works. Tamari is gluten-free and slightly richer; regular low-sodium soy sauce is a straight swap.
- Dry white wine: If you’d rather skip it, use an extra splash of vegetable broth plus a small squeeze of lemon juice to get the acidity back.
- Vegan mozzarella: A meltable block-style vegan mozzarella (Miyoko’s, Violife, or similar) works best under the broiler. Shredded versions from a bag tend to dry out rather than bubble — skip the garnish version and go with sliced.
- Cashew cream: Optional, but if you want a slightly silkier broth, two tablespoons stirred in at the end does the job. Oat-based cooking cream works too.
- Mushroom powder: A teaspoon of dried porcini powder or blended dried shiitake adds another layer of umami if you have it. Not essential, but a good use of the odds and ends in your pantry.
What can go wrong
- Onions burning instead of caramelizing: If the pan gets too hot, the onions scorch on the outside while staying raw inside. Keep the heat at medium-low and stir every few minutes. A heavy-bottomed Dutch oven helps distribute heat evenly.
- Broth tasting flat: This usually means under-seasoned onions or low-quality vegetable broth. Taste the broth before adding the balsamic and tamari — if it already tastes watery, reduce it uncovered for 10 minutes before finishing.
- Bread sinking into the soup: The toast needs to be genuinely dry and crisp before it goes on top. If your baguette slices are soft or fresh, toast them longer — a slightly stale slice actually holds up better under the broiler.
- Cheese not browning under the broiler: Vegan cheeses vary a lot. If yours isn’t browning after 3–4 minutes, move the rack closer to the broiler element. Watch it — it can go from pale to scorched quickly.
- Soup cooling too fast in the bowl: Oven-safe crocks hold heat much better than regular bowls. If you’re using standard bowls, warm them with hot water for a minute before ladling in the soup.
Vegan French Onion Soup
Equipment
- Dutch oven or heavy-bottomed soup pot
- Wooden spoon
- Ladle
- Baking tray
Ingredients
Soup Base
- 2 tablespoons olive oil Extra virgin for best flavor
- 4 cups yellow onions Thinly sliced, preferably organic
- 1 teaspoon sea salt
- 3 cloves garlic Minced
- ½ cup dry white wine Optional, but recommended for depth
- 1 tablespoon balsamic vinegar
- 1 tablespoon tamari Or low-sodium soy sauce
- 4 cups vegetable broth Preferably homemade or low-sodium
- 2 teaspoons fresh thyme Or 1 teaspoon dried
- 1 whole bay leaf
Topping
- 4 slices baguette Day-old, toasted
- 1 cup vegan mozzarella cheese Shredded, choose a meltable brand like Miyoko’s
Instructions
- In a large Dutch oven over medium-low heat, add the olive oil and sliced onions. Sprinkle with salt and stir to coat. Cook for 30–40 minutes, stirring every few minutes, until the onions are deep golden brown and caramelized. Reduce heat if onions begin to burn.
- Once the onions are caramelized, stir in the minced garlic and cook for 1 minute until fragrant.
- Deglaze the pot with dry white wine (if using), scraping up any browned bits. Let it simmer for 2–3 minutes to cook off the alcohol.
- Add the balsamic vinegar and tamari. Stir well to integrate flavors.
- Pour in the vegetable broth, add thyme and bay leaf, and raise the heat to bring the soup to a gentle simmer. Reduce heat and cook uncovered for 30 minutes.
- Meanwhile, toast baguette slices until crisp. Top each slice with shredded vegan mozzarella and place under a broiler at 400°F (200°C) for 5–6 minutes, or until melted and bubbling.
- Remove bay leaf before serving. Ladle soup into bowls, top each with the cheesy toast, and serve hot.
Notes
- Add a splash of soy milk or cashew cream for extra silkiness
- If skipping wine, add an extra teaspoon of tamari or mushroom powder for umami
- You can make the caramelized onions up to 3 days in advance and refrigerate
Nutrition
Your questions, answered
Can I make this ahead of time?
Yes — the soup base keeps well in the refrigerator for up to four days. Store it without the bread and cheese, then reheat on the stovetop, ladle into oven-safe bowls, add the toast and cheese, and broil just before serving.
Will people who eat meat actually like this?
Most do, especially if you don’t announce the substitutions upfront. The caramelized onion base and umami-forward broth hit the same savory notes as the traditional version — the main thing people notice is that it’s slightly lighter, which most find pleasant rather than lacking.
What if I can’t find a meltable vegan cheese?
A thick smear of cashew-based vegan cream cheese on the toast is a workable alternative — it won’t stretch and bubble the same way, but it browns nicely under the broiler and adds richness. Avoid nutritional yeast sprinkled on top as a standalone substitute; it doesn’t melt and the texture is off.
Can I use a different type of onion?
Yellow onions are the standard choice and caramelize reliably. Sweet onions like Vidalia work and go a little softer and sweeter. Red onions caramelize fine but turn the broth an odd color — they’re not ideal here.
Do I need oven-safe bowls for the broiling step?
You do need bowls that can go under the broiler — standard ceramic or glass bowls that aren’t rated for broiler use can crack. If you don’t have oven-safe crocks, broil the cheese toast on a baking sheet separately and lay it on top of the soup right before serving.
More plant-based recipes to try
- French Vegan Cassoulet
- Vegan Polenta Mushroom Bliss
- Smoky Spanish Chickpea Stew
- Golden Curried Parsnip Soup