Vegetarian French Onion Soup

Vegetarian french onion soup. One of my all-time favorite soups.

Probably because it includes cheese and bread… Also because it reminds me of our trip to Mexico two years ago (has it really been two years!?).

You may be wondering why I think of Mexico whenever I have French onion soup? It’s not exactly a Mexican dish… Let me explain.

Shaun won a trip from work two years ago and we treated ourselves to a beautiful resort in Mexico. At our resort, we had a few restaurants to choose from every night, all of them included in our stay. Of course, we tried them all (except for the sushi place… Sorry, I’m not a fan of sushi). There was an Italian, a French and an American restaurant, all of which were amazing. Our favorite dish was the French onion soup from the French restaurant. It was my first time trying this soup and it was amazing. Especially since instead of a baguette, the soup was topped with puff pastry… I wish I could go back to that resort just for the soup.

Naturally, I wanted to recreate the soup. That’s when I figured out that traditional French onion soup is made with beef broth (oups), so I decided to try it out with vegetable broth. I since made many French onion soup recipes, but I knew I wanted to create my own.

There are a few things I changed with mine. First, I used mushroom broth. Trust me, this takes it to a whole new level. A lot better than vegetable broth in my opinion. However, since mushroom broth doesn’t come unsalted or low-sodium around here, I used half unsalted vegetable broth and half mushroom broth. It tasted perfect to me!

Next, I tried to reduce the amount of butter/margarine used as much as possible without having the onions stick to the saucepan. I found that 4 tablespoons was a good amount to use.

Finally, since gruyere cheese is ridiculously expensive, I decided to use old white cheddar cheese. If you prefer to use gruyere, then go for it! It’s delicious and a little more traditional. If you’re like me and you’re cheap when it comes to buying cheese, then go for white cheddar. It has a strong taste and goes perfectly with the caramelized onions and mushroom broth. It’s absolutely delicious! Swiss and mozzarella would work too.

Here’s how the soup goes: First, you need to caramelize your onions. This is what takes a little more time and attention as you need to stir every few minutes for 30 minutes. With just a little patience, you’ll end up with a perfect soup. Trust me, it’s worth the time!

Vegetarian French Onion Soup | Unsweetened Caroline

This is what it looks like after about 15 minutes:

And now after 30 minutes:

Vegetarian French Onion Soup | Unsweetened Caroline

Your onions should be very soft and lightly golden.

Next, add the wine to deglaze.

Vegetarian French Onion Soup | Unsweetened Caroline
Vegetarian French Onion Soup | Unsweetened Caroline
Vegetarian French Onion Soup | Unsweetened Caroline

When your onions are caramelized and you’ve added the wine, add the remaining ingredients. Bring everything to a boil, simmer for 10 minutes, then transfer to oven-safe bowls. Put a slice of fresh bread on top of your soup (I like to use my homemade bread, but fresh baguette works too!) and a generous sprinkle of cheese. Again, I use old white cheddar, but Gruyere is just as delicious and a little more traditional. The bottom line is: Use what you have on hand. This soup is versatile and I guarantee it will be delicious no matter what. As long as your onions are well caramelized and that you have some bread and cheese on top. I mean, cheese and bread make everything better.

I included a few notes with the recipe to give you different options when it comes to the ingredients.

I hope you enjoy this recipe as much as we do! Although it doesn’t contain beef broth or puff pastry, I can guarantee you that it’s just as delicious and comforting on a cold winter day. 🙂

Vegetarian French Onion Soup | Unsweetened Caroline
Vegetarian French Onion Soup | Unsweetened Caroline
Vegetarian French Onion Soup | Unsweetened Caroline
Vegetarian French Onion Soup | Unsweetened Caroline

Vegetarian French Onion Soup

This onion soup is made vegetarian by using mushroom broth instead of beef broth, but don’t worry, it tastes just as good! Top with fresh bread and a generous amount of cheese, bake until the cheese has melted and has turned lightly golden and bubbly. Enjoy every spoonful. 
Course Appetizer, Soup
Cuisine French, vegan, vegetarian
Prep Time 15 minutes
Cook Time 50 minutes
Total Time 1 hour 5 minutes
Servings 4


  • 4 tablespoons butter or soft margarine
  • 4 medium yellow onions, peeled and sliced into half-moons
  • 2 large garlic cloves
  • 1/2 cup dry red wine
  • 1 tablespoon flour
  • 8 cups mushroom or vegetable broth, low-sodium
  • 1 teaspoon Worcestershire sauce (optional)
  • 3 sprigs fresh thyme
  • 1 bay leaf
  • 1 teaspoon fine grain sea salt, to taste
  • french bread, such as baguette
  • 1 1/2 cups Grated cheese (old white cheddar, gruyere, swiss or mozzarella works)


  • Heat butter/margarine in a large saucepan over medium heat. 
  • Add onions and stir to coat with butter/margarine. Cook for 30 minutes, stirring every few minutes to avoid sticking. The onions should slowly brown, without getting burnt.
  • After 30 minutes. stir in the garlic and salt and cook for another minute. Using a wooden spoon, scrape up any pieces sticking to the pan.
  • Slowly stir in the wine to deglaze the pan. Stir in the flour, followed by the broth, Worcestershire sauce, thyme and bay leaf.
  • Bring the soup to a boil, then reduce heat to low-medium and simmer for 10 minutes, covered. Meanwhile, preheat oven to 400F. 
  • Remove the sprigs of thyme and bay leaf using a spoon. Spoon the soup in oven-safe bowls. Top with a slice of french bread and a sprinkle of cheese (approximately 1/4 cup on each).
  • Bake for 6 minutes, then broil until golden and bubbly, being careful it doesn’t burn. Serve immediately.


Use dry red or white wine, whichever one you prefer.
I use whole wheat flour, but white flour works as well. I haven’t tried a gluten-free flour, but for a gluten-free option, omit the flour.
Feel free to use beef or vegetable broth if preferred. I tend to use half mushroom and half vegetable broth as my vegetable broth is salt-free and it helps reduce the salt in the recipe. You can use low-sodium mushroom broth if available. Adjust the salt to taste.
Store leftover soup in the fridge. When ready to eat, heat up your soup, then transfer to an oven safe bowl and bake with the bread and cheese as directed. I don’t recommend storing leftovers with the baked bread and cheese on top.

If you try this recipe, make sure to tag your photo #unsweetenedcaroline on Instagram, Facebook and Twitter! Don’t forget to also tag me @unsweetened.caroline on Instagram so I can see your creations!

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