Vegetarian French Onion Soup
Rich and savory French onion soup topped with crispy croutons and melted cheese might just be one of my favorite recipes of all time! This vegetarian version gets all its flavor from caramelized onions, homemade mushroom stock, fresh thyme, and Worcestershire sauce. You wouldn’t even know it’s made without beef broth!
A few simple ingredients; onions, bread, and cheese, are transformed into a rich and luxurious soup that is a staple in any French bistro! I probably served 1,000 bowls of this cheesy caramelized onion soup when I was a line cook at a busy French restaurant! It was hands down the most popular menu item.
French Onion Soup is traditionally made with beef or veal stock making it, for obvious reasons, not at all vegetarian friendly. My version trades beef stock for umami-rich mushroom stock infused with garlic, onion, and thyme. Trust me, it’s just as good, if not better than the classic!
Serve this indulgent soup with my Everyday Dinner Salad with zesty caper-cornichon vinaigrette! It’s the perfect side dish to cut through the richness of the soup!
Vegetarian French Onion Soup Ingredients:
Here’s everything you need to make this recipe: onions (duh!), butter, flour, mushroom stock (homemade or store-bought), thyme, sherry, vegan Worcestershire, vinegar, cheese, and a baguette.
A note about vegetarian cheese:
Did you know that not all cheese is vegetarian-friendly? Many kinds of cheese are made with “rennet” which is an enzyme that comes from the stomachs of cows. Luckily, there are a few brands that make “vegetarian-safe” cheeses free from rennet. While Gruyére and Emmental are the most traditional cheeses to use for French onion soup I recommend choosing an organic swiss, or even white cheddar cheese for a vegetarian-safe substitute. Organic Valley, Horizon, Applegate, and Tillamook all offer vegetarian cheeses and are readily available at most supermarkets.
Homemade Mushroom Stock Ingredients:
FYI you don’t have to make your own stock for this recipe. In a pinch, boxed stock will totally work. That being said, it is actually very easy to make from scratch and I do think the flavor makes it worth the extra trouble. I have included my mushroom stock recipe below in case you want to give it a go. The ingredients you’ll need are mushrooms (fresh and dried), onion, garlic, carrot, thyme, parsley, cold water, salt, and pepper.
Recipe Step by Step
Step 1. Caramelize the Onions
Melt the butter in a large soup pot, add in the sliced onions and a generous pinch of salt. Cook for about 10 minutes, stirring occasionally so that the onion does not burn. Reduce heat to medium-low to caramelize gradually. FYI wrote an entire post on how to make rich, sweet, and deeply golden brown caramelized onions! Click here to check it out!
Step 2. Deglaze, Season and Simmer
When the onions have caramelized to a golden brown color, add in the flour and cook, stirring, for 1 minute. Next, deglaze with the dry sherry. Continue stirring until most of the sherry is evaporated then add the thyme, Worcestershire, vinegar, and mushroom stock. Simmer on low for 20-30 minutes. Season to taste with salt and pepper.
Step 3. Make the Croutons
Preheat the oven to 400°F. While the soup is simmering, slice the baguette into 1/4-inch thick pieces and arrange them in a single layer on a baking sheet. Bake for 5 minutes, until the bread is toasted and golden around the edges. Remove and set aside.
Step 4. Broil
Switch the oven to broil. Ladle the soup into oven-safe bowls. Add 1-2 slices of toasted baguette to each and top with two slices of cheese. Place each soup bowl on a baking sheet and transfer to the oven, broil until bubbly and golden brown, 2 to 3 minutes. Serve immediately!
FAQ’s and Recipe Tips
Worcestershire sauce traditionally contains anchovies. The icon brown paper-wrapped bottle of Lea & Perrins is a no-go for vegetarians. Instead grab the vegan version from Annie’s.
Any dry white or red wine can be used in place of sherry in this recipe. If you prefer to not cook with alcohol you can simply omit it.
If you don’t have oven-proof bowls you can skip the broiling by melting the cheese on top of the toast in the oven and then place them on top of the soup just before serving.
Nope! You can use boxed mushroom or vegetable stock.
Not all cheese is vegetarian-friendly! Many kinds of cheese are made with “rennet” which is an enzyme that comes from the stomachs of cows. Luckily, there are a few brands that make “vegetarian-safe” cheeses free from rennet. Organic Valley, Horizon, Applegate, and Tillamook all offer vegetarian cheeses and are readily available at most supermarkets.
Check out more great recipes:
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Vegetarian French Onion Soup
Ingredients
Vegetarian French Onion Soup
- 6 c mushroom stock homemade or store-bought
- 6 medium yellow onions peeled, halved, and thinly sliced
- 1/4 c butter
- 1 tbsp flour
- 1/2 c dry sherry
- 4 sprigs thyme
- 2 tbsp Worcestershire sauce make sure to buy vegetarian, see note
- 1 tbsp vinegar sherry, white wine, champagne, or red wine
- 8 slices swiss or gruyére cheese
- 1 baguette
- salt and pepper
Homemade Mushroom Stock
- 1 tbsp olive oil
- 1 medium yellow onion peeled and halved
- 2 carrots peeled, stem removed
- 1 head garlic
- 8 oz button mushrooms
- 1 oz dried shiitake mushroom
- 3 sprigs thyme
- 1 small handful parsley
- 1 tbsp black peppercorns
- 8 c cold water
- salt
Instructions
Soup
- Melt the butter in a large soup pot over medium-high heat, then add in the sliced onions and a generous pinch of salt. Cook on medium-high heat for about 10 minutes, stirring occasionally so that the onion does not burn. Reduce heat to medium-low to caramelize gradually. This will take some time, about 30 minutes.
- When the onions have caramelized to a golden brown color, add in the flour and cook, stirring, for 1 minute. Next, deglaze with the dry sherry. Continue stirring until most of the sherry is evaporated then add the thyme, Worcestershire, vinegar, and mushroom stock. Simmer on low for 20-30 minutes. Season to taste with salt and pepper.
- Preheat the oven to 400°F. While the soup is simmering, slice the baguette into 1/4-inch thick pieces and arrange them in a single layer on a baking sheet. Bake for 5 minutes, until the bread is toasted and golden around the edges. Remove and set aside.
- Switch the oven to broil. Ladle the soup into oven-safe bowls. Add 1-2 slices of toasted baguette to each and top with two slices of cheese. Place each soup bowl on a baking sheet and transfer to the oven, broil until bubbly and golden brown, 2 to 3 minutes. Serve immediately!
Homemade Mushroom Stock
- Heat the olive oil in a large stock put over medium-high heat. Add the onion, mushroom, and carrot to the pot. Sauté 5-10 minutes, stirring frequently.
- Add the remaining ingredients as well as a generous pinch of salt then cover with 8 cups of cold water. Bring the stock to a boil, then turn the heat to low and simmer, uncovered, for 1 hour. Pour the stock through a strainer, pressing as much liquid as you can from the vegetables, then discard them.
I’ve made this 4x now. Flawless recipe. Thank you
SO good! My SIL is vegetarian so I’m making this for her next week!
I’m so glad! Thanks, Denise!
I LOVE that this doesn’t use beef broth! I made the homemade mushroom broth and it came out so good!