Vegetarian French Onion Soup

This vegetarian French onion soup is the ultimate comfort food! It’s got the rich flavor of the classic, topped with a golden crust of cheese.

Vegetarian French Onion Soup

There’s just something about silky caramelized onions topped golden, crusty cheese that takes your breath away every time. This is classic French cooking at its finest. It’s not just the flavor. It’s the promise that while the outside world is cold and brutal, every spoonful of French onion soup is pure bliss. This vegetarian French onion soup is our spin on the classic: it’s so full of rich, nuanced flavor you won’t miss the traditional beef broth. It’s a bit of a project: but it’s worth every moment of the prep. Promise!

How to make French onion soup: an overview

The modern version of French onion soup was invented in Paris in the 1700’s. It was introduced in the US in the 1860’s in a New York restaurant, and it’s been popular ever since! Of course once you take a bite, you’ll know why it’s a classic even today.

You’ll need about 1.25 hours to make this vegetarian French onion soup. But it is 100% worth the effort, and you can make a few components in advance as time savers. Make it on a cozy day when you have time to prep, or do the advanced prep if you’re serving for a dinner party.

Caramelize the onions1 hour
Make the vegetarian broth30 minutes (concurrent while cooking onions)
Make the soup15 minutes
Vegetarian French onion soup

The key to vegetarian French onion soup: homemade broth

Here’s one important thing to note. Vegetable broths and stocks vary widely in flavor and quality. Try it in a French onion soup, and most purchased veggie broth comes out sweet: not savory like you’d expect! Trust us, we tested a few times and it did not taste right.

Here’s what you’ll have to do: make a homemade vegetable broth! It might sound like overkill, but it makes for just the right flavor. When Alex and I tried it with this homemade broth, we were amazed by the flavor. Don’t skip this step!

Of course, if you want a classic French onion soup: just use beef broth! You can make the same recipe without that step and of course, it tastes great too.

Caramelizing onions: a few tips

The main time-consuming step for vegetarian French onion soup is caramelizing the onions! Sure, you can saute onions in about 10 minutes. But to get them fully dark brown and caramelized takes about 1 hour. Here are the basic steps, and a graphic that shows the color of the onions each phase!

  • Thinly slice the onions.
  • Sauté the onions in butter for 10 minutes on medium high.
  • Reduce the heat to medium low, add salt and saute for 40 to 45 minutes until deep brown and very soft.
How to caramelize onions

Dry sherry brings big flavor (or use white wine)

This vegetarian French onion soup uses dry sherry to bring in complexity and intrigue into the flavor. What is it, and what’s a substitute?

  • Sherry is a fortified wine made in Spain that’s made by adding grape liquor to white wine. The flavor is sharp, with a scent of apple cider and a very dry finish. It’s worth finding for this recipe if you don’t have it already.
  • How long does sherry last? An opened bottle of sherry lasts in the refrigerator for 2 to 3 months.
  • What’s a substitute for sherry? Don’t’ have it? You can use a dry white wine instead (make sure it’s not a sweet wine).

The crouton topping: broil or bake!

The last component to a great vegetarian French onion soup is the crouton topping! That is: it’s topped bread and cheese, broiled to golden perfection. There are a few techniques to achieve this, but I love the one that Alex devised using both Swiss cheese and grated Parmesan. Here’s what to do:

  • Place the soup into small oven-safe bowls or ramekins. This is key! Make sure you have some small serving bowls: typically this soup is not served in large vessels.
  • Add 1/2 inch slices of bread, then Swiss or Gruyere and grated Parmesan cheese. The two cheese really makes the perfect melting. Remember: grated Parm is the kind that looks like snow (don’t use shredded).
  • Broil for 2 minutes or bake 20 minutes at 400 degrees. The broiling method here is much easier and quicker: we prefer it! But if you don’t have a broiler, go the oven route.
How to make French onion soup

Make ahead tips for vegetarian French onion soup

Last tip before we get to this (very tasty) recipe: here’s how to speed it up! You can make both of the main components in advance:

  • Caramelize the onions in advance. This makes the prep time take next to nothing! Caramelize the onions, then refrigerate until serving. Bring to warm before you pick up in the soup recipe.
  • Make the homemade broth in advance. Same idea! You can refrigerate until serving, then warm it up and pick right back up in the recipe.

What to serve with French onion soup

Here’s a final important thing to note about French onion soup: it’s not intended as a full meal. It’s generally served as an appetizer to an elegant meal, or as a lunch. How to make it into a light meal? Here’s what to add:

Vegetarian French onion soup recipe

This vegetarian French onion soup is…

Vegetarian. For gluten-free, use gluten-free bread.

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Vegetarian French Onion Soup

Vegetarian French Onion Soup


1 Star2 Stars3 Stars4 Stars5 Stars (10 votes, average: 4.80 out of 5)

  • Author: Sonja Overhiser
  • Prep Time: 5 minutes
  • Cook Time: 1 hour 15 minutes
  • Total Time: 1 hour 20 minutes
  • Yield: 6 1x
  • Diet: Vegetarian

Description

This vegetarian French onion soup is the ultimate comfort food! It’s got the rich flavor of the classic, topped with a golden crust of cheese.


Ingredients

Scale

For the caramelized onions

  • 2 tablespoons butter
  • 3 pounds yellow onions (5 medium)
  • 1 teaspoon kosher salt
  • 1/2 cup dry sherry (or white wine)
  • 1 tablespoon flour

For the soup

  • 2 tablespoons butter
  • 8 ounces mushrooms
  • 1 carrot
  • 2 celery ribs
  • 6 garlic cloves
  • 9 cups water, divided
  • 2 tablespoons tomato paste
  • 1 teaspoon each garlic powder and onion powder
  • 1 teaspoon vegan Worcestershire sauce (purchased or use this substitute)
  • 2 teaspoons kosher salt
  • 6 slices Swiss or Gruyere cheese (or shredded)
  • 6 tablespoons grated Parmesan cheese
  • 6 large or 12 small slices bread, sliced about 1/2” thick

Instructions

  1. Caramelize the onions: Thinly slice the onions about 1/8-inch thick (we used a French cut by slicing stem to root; go to minute 1:40 of the linked video for a tutorial). In a soup pot, heat the butter over medium high heat. Add the onions and sauté for 8 to 10 minutes, stirring often, until very soft and just starting to brown on the bottom. Reduce to medium-low heat and stir in the kosher salt. Cook for 40 to 45 minutes, stirring every 5 to 10 minutes and adjusting the heat so they continue to cook slowly without burning. The onions will change from raw to golden to light brown to very dark brown, and reduce in volume by about 1/4. (Make ahead tip: Make the caramelized onions in advance and refrigerate until ready to make the soup. Reheat in a pan and go to step 3.)
  2. Meanwhile, make the homemade broth: Slice the mushrooms. Wash and cut the carrot in half length-wise, then into large chunks. Cut the celery into large pieces. Smash and peel the garlic. In a second pot, heat the butter over medium heat. Add the mushrooms and sauté until browned, about 6 to 7 minutes. Add 8 cups water, kosher salt, vegetables, tomato paste, garlic powder, onion powder, and Worcestershire sauce. Bring to a boil and simmer for 30 minutes. (Make ahead: Make the broth in advance and refrigerate until serving. Then warm before proceeding to Step 3.)
  3. Simmer the soup: When onions are very reduced and dark brown, stir in the sherry and deglaze the pan by scrape all the bits off the bottom of the pan. Sprinkle with the flour and stir until the onions are coated. Strain the homemade broth into the onions (discarding the vegetables). Add the remaining 1 cup water and bring to a simmer for 2 minutes.
  4. Broil the topping: Place the soup into 6 oven-safe small bowls or ramekins. Preheat a broiler to high or an oven to 400 degrees Fahrenheit. Top with bread slices (about 1/2-inch thick), 1 slice Swiss or Gruyere cheese, and 1 tablespoon grated Parmesan per bowl. Broil 1 to 3 minutes (or bake for 20 minutes) until the cheese is melted and browned. Place on a plate and serve immediately, taking care since the bowls are very hot. 
  • Category: Main Dish
  • Method: Stovetop
  • Cuisine: French

Keywords: Vegetarian French onion soup, French onion soup, How to make French onion soup

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About the Authors

Sonja Overhiser

Cookbook Author and writer

Sonja Overhiser is author of Pretty Simple Cooking, named one of the best healthy cookbooks of 2018. She’s host of the food podcast Small Bites and founder of the food blog A Couple Cooks. Featured from the TODAY Show to Bon Appetit, Sonja seeks to inspire adventurous eating to make the world a better place one bite at a time.

Alex Overhiser

Cookbook Author and photographer

Alex Overhiser is an acclaimed food photographer and author based in Indianapolis. He’s host of the food podcast Small Bites and founder of the recipe website A Couple Cooks. Featured from the TODAY Show to Bon Appetit, Alex is author of Pretty Simple Cooking, named one of the best vegetarian cookbooks by Epicurious.

4 Comments

  • Reply
    John
    February 5, 2021 at 10:35 am

    Are the vegetables strained from the stock before making the onion soup?

    • Reply
      Alex Overhiser
      February 5, 2021 at 2:20 pm

      Yes (step 3)

  • Reply
    Ashley
    February 7, 2021 at 11:08 pm

    Am I missing the step when the Worcestershire/tomato paste/garlic & onion powders are added?

    • Reply
      Sonja Overhiser
      February 8, 2021 at 9:35 am

      This was a typo and is fixed! Thank you!

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