Slow-cooked onions, mushroom broth, and gooey cheese — this Vegetarian French Onion Soup is comfort food that hits right in the heart.

this recipe

You ever get hit with a craving that just won’t quit? That was me last winter. It was one of those gray, moody evenings when the rain kept tapping on the windows and my kitchen felt just a little too quiet. I wanted something cozy. Something slow. Something that smelled like butter and home.

My first thought? French Onion Soup — that deeply rich, cheesy bowl of nostalgia. But then reality hit me: no beef broth in sight. Just a carton of mushroom broth I’d bought weeks ago for… I don’t even remember what. I almost gave up right there. But then I thought, you know what, let’s see what happens.

So I grabbed a mountain of onions (seriously, it looked like I was about to open a diner), threw them in a pot with butter, and just started stirring. Slowly. I put on an old playlist — the kind you only listen to when you’re alone — and let the smell of caramelizing onions take over the house. After about an hour, I added that mushroom broth, a splash of white wine (and okay, maybe a sip for myself), and when I finally tasted it… wow. It was everything I wanted and somehow better.

Now it’s my go-to when I want something that feels like a hug in food form. It’s rich without being heavy, savory without the meat, and that cheesy crust on top? Pure magic. I’ve made it for friends who swore they’d never like a vegetarian version — and guess what? Not a single spoonful left.

Why You’ll Love This Vegetarian French Onion Soup Recipe?

This soup is one of those rare dishes that feels like both a warm blanket and a small victory. It’s slow food, the kind that makes you feel a little proud of yourself when it’s done. You get this deep, caramelized sweetness from the onions, a subtle earthiness from the mushroom broth, and that gooey, golden cheese topping that’s honestly just showing off.

And here’s the thing — it’s not complicated. It just sounds fancy. You’re basically letting onions do their thing for an hour while you half-watch a show or scroll your phone. Then you throw in the broth, toast some bread, melt some cheese, and suddenly you’ve got this restaurant-level dish that makes everyone at the table go quiet for a second before the inevitable, “Oh my god, this is so good.”

If you love cozy meals that feel a little indulgent but still simple, this Vegetarian French Onion Soup is your new best friend.

Ingredient Notes:

Alright, before you dive in, let’s talk about the essentials — because this soup is all about simple ingredients done right.

• Onions: Yellow onions are the MVP here. They caramelize beautifully. If you use red onions, it’ll taste fine, but it’ll look… weird.

• Butter and Oil: The duo that keeps your onions from burning. Don’t skip one or the other. Butter for flavor, oil for stability.

• Mushroom Broth: Don’t underestimate this one. It gives that deep, almost beefy flavor — without the beef.

• White Wine: Sauvignon Blanc or Pinot Grigio work great. Nothing sweet. And yes, you can sip while cooking — it’s practically required.

• Cheese: Gruyère is the classic, but I’ve mixed it with Swiss, and it’s glorious. Melty, nutty, stretchy — all the good things.

• Worcestershire & Balsamic: A little of each gives this soup that tangy depth that makes you go, what is that flavor? (in a good way).

Pro tip: When you think the onions are done, give them 10 more minutes. That’s when the flavor goes from “good” to “you’ll be licking the spoon.”

How To Make Vegetarian French Onion Soup?

Step 1: Caramelize the Onions
This is the soul of the soup, so don’t rush it. Melt your butter and oil in a big pot, toss in those sliced onions, and just… breathe. They’ll cook down slowly, shrink, and turn golden over about an hour. Stir every few minutes, scrape the brown bits off the bottom (that’s flavor!), and let the smell remind you that patience pays off.

Step 2: Deglaze with Wine
Pour in your white wine and let it sizzle. Scrape up the bits from the bottom — those are gold. Let it simmer until most of the wine’s cooked off, and your kitchen smells like a fancy bistro.

Step 3: Add the Flour
Sprinkle in the flour and stir until it disappears. It’s just there to thicken things slightly. Cook it out for about 3 minutes so it doesn’t taste like dough.

Step 4: Add Broth & Herbs
Now comes the good stuff. Pour in your mushroom broth, toss in the thyme and bay leaves, and season with salt and pepper. Bring it to a gentle simmer and let it bubble away for about 15 minutes. Your house will smell like comfort incarnate.

Step 5: Finish It Off
Remove the herbs (they’ve done their job) and stir in the Worcestershire and balsamic. Taste it. Adjust the salt. Maybe add a bit more pepper because, why not?

Step 6: Broil the Toppings
Ladle the soup into oven-safe bowls. Top each with baguette slices, a slice of Swiss, and a handful of Gruyère. Pop them under the broiler until the cheese is bubbly and golden — but don’t blink, it burns fast!

Then take a moment. Just look at it — the melted cheese, the bubbling edges, the smell. You did that.

Storage Options:

If by some miracle you have leftovers (I doubt it), they’ll keep beautifully for up to four days in the fridge. Just warm it gently on the stove when you’re ready. If you’re freezing it, skip the bread and cheese — just freeze the broth part, then reheat and finish fresh later. It’s actually kind of genius to make a double batch for future rainy nights.

Variations and Substitutions:

The beauty of this Vegetarian French Onion Soup is that it’s flexible. You can make it your own without messing up the soul of it.

• Make it Vegan: Use plant-based butter and vegan cheese — and you’re golden.

• Add Mushrooms: If you want extra umami, toss in some sautéed mushrooms with the onions.

• Gluten-Free: Use gluten-free flour and baguette. It works perfectly.

• No Wine? No problem. Use more broth and add a little lemon juice or apple cider vinegar for brightness.

• Cheese Swap: Comté, provolone, or even mozzarella all work. Play around — it’s not that serious.

I’ve even added a pinch of smoked paprika once — not traditional, but holy wow, it was good.

What to Serve with Vegetarian French Onion Soup?

Honestly? It’s pretty perfect on its own. But if you want to make it a full meal:

• Crisp Salad: Something light with lemon vinaigrette.

• Roasted Veggies: Especially carrots or Brussels sprouts.

• Crusty Bread: Always, always more bread.

• Wine: Whatever’s left from cooking. You earned it.

This soup’s also a great starter for a cozy dinner party — or a lazy Sunday dinner where pants with buttons are optional.

Frequently Asked Questions:

Can I make it ahead?
Totally. The flavor actually gets better the next day. Just reheat it gently before broiling with fresh cheese.

Can I skip the cheese?
You can, but… why would you? The cheese is kind of the whole experience.

What kind of pot works best?
A Dutch oven is ideal, but honestly, any heavy-bottomed pot will do. Just don’t use something thin — those onions need even heat and love.

This Vegetarian French Onion Soup is one of those recipes that just feels personal. It’s slow, imperfect, and completely worth every minute. It’s the kind of dish that teaches you something — about patience, about flavor, maybe even about yourself.

So pour yourself a glass of wine, grab that pile of onions, and make it tonight. Just don’t forget to taste as you go, and maybe sneak a little cheese before it hits the oven. I won’t tell.

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Vegetarian French Onion Soup

Prep Time 10 minutes mins

Cook Time 1 hour hr 20 minutes mins

Total Time 1 hour hr 30 minutes mins

This Vegetarian French Onion Soup features deeply caramelized onions simmered in rich mushroom broth, finished with melted Swiss and Gruyère cheese for a comforting, meat-free classic.

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6 Servings

Ingredients

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• 4 tablespoons unsalted butter
• 2 tablespoons avocado oil or other neutral oil
• 4 large yellow onions 8–10 cups, sliced ⅛-inch thick
• ½ cup dry white wine such as Sauvignon Blanc
• 2 tablespoons all-purpose flour
• 8 cups mushroom broth
• 3 sprigs fresh thyme
• 2 dried bay leaves
• 1½ teaspoons salt
• ½ teaspoon ground black pepper
• 1 tablespoon vegan Worcestershire sauce
• 2 teaspoons balsamic vinegar
• 1 French baguette sliced into 1-inch pieces
• 6 slices Swiss cheese about 6 ounces
• 1½ cups shredded Gruyère cheese about 6 ounces

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Instructions

 

Caramelize the Onions

1. In a 5-quart Dutch oven or large heavy-bottomed pot, melt the butter and oil over medium heat. Add the sliced onions and stir to evenly coat them with the fat. Cook for approximately 60 minutes, stirring every few minutes with a wooden spoon. The onions should gradually soften, reduce in volume, and develop a deep golden color. Scrape any brown bits from the bottom of the pot as they appear to prevent burning and to enhance flavor.

Deglaze the Pot

1. Increase the heat to medium-high and pour in the white wine. Using a wooden spoon, scrape up any caramelized bits from the bottom and sides of the pot. Allow the wine to simmer for about 4 minutes, or until most of the liquid has evaporated.

Add the Flour

1. Sprinkle the flour over the onions, stirring continuously until fully incorporated. Cook for 3–4 minutes to remove any raw flour taste, ensuring the mixture thickens slightly.

Add the Broth and Seasoning

1. Pour in the mushroom broth, stirring to deglaze any remaining bits. Add the thyme, bay leaves, salt, and black pepper. Bring the soup to a gentle boil, then reduce the heat to medium-low and let it simmer uncovered for 15 minutes.

Finish the Soup

1. Remove the thyme stems and bay leaves. Stir in the vegan Worcestershire sauce and balsamic vinegar. Adjust seasoning to taste.

Prepare for Broiling

1. Preheat the oven broiler and position the rack on the top level. Line a baking sheet with aluminum foil and arrange six oven-safe bowls or crocks on the sheet.

Broil and Serve

1. Ladle the soup evenly into the bowls, leaving about ½ inch of space at the top. Place 1–2 slices of baguette over each portion, followed by one slice of Swiss cheese and a generous sprinkle of shredded Gruyère. Carefully transfer the baking sheet to the oven and broil for 2–5 minutes, watching closely until the cheese is bubbling and golden brown.
2. Remove from the oven and serve immediately while hot.

Notes

To make this Vegetarian French Onion Soup gluten-free, replace the all-purpose flour with a certified gluten-free flour blend or cornstarch (use 1 tablespoon). Substitute the baguette with a gluten-free loaf or sliced gluten-free bread. Double-check that your Worcestershire sauce is gluten-free, as some brands may contain malt vinegar derived from barley. The rest of the ingredients, including mushroom broth and cheese, are naturally gluten-free.

Bitty

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Bitty

I’m Bitty, owner of nodashofgluten.com, where I share simple, delicious recipes for all tastes, including gluten-free. Check out my “About Me” page for more info!

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