Vegetarian French Onion Soup Recipe

Vegetarian French Onion Soup

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Is there anything more comforting than sitting down to a rich, steaming bowl of soup to soothe your soul? And what better and richer than French onion soup? In this post, I bring you my favorite way to make a vegetarian French onion soup version, which you can also vegan-ize as well. From caramelizing the onions to perfectly toasting the bread topping, I take you step by step in making this delicious, savory and heart warming recipe.

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Classic French onion soup

Traditional French onion soup, or soupe à l’oignon or Gratinée des Halles, is made with beef stock and onions. It’s usually served “gratinéed with croutons and cheese on top of a large piece of bread”. In this version, I use vegetable broth instead of the beef broth, and it still retains its richness.

French onion soup also uses caramelization of the sugars in onions to develop it’s unique flavor and color. We’ll look more closely into caramelizing onions below.

What liquor do you put in French onion soup?

Classic French onion soup is made with wine or sherry to bring out the beef flavor of the broth. In this vegetarian French onion soup recipe, I used sweet red wine, but you can use whichever you like best.

Dry red wine, such as a good quality Pinot Grigio, Merlot or Pinot Noir are good options for this soup. I’ve heard somewhere that if you can’t drink it, don’t cook with it, and it’s actually good advice!

What can I use instead of wine in french onion soup?

You can replace the wine with extra vegetable broth. Or you can also use alcohol free wine.

What are the bowls called for French onion soup?

According to this article from The Kitchn (which I love), “French onion soup is traditionally served in lionhead bowls, which are deep but not very wide porcelain bowls”. These bowls are great because their handles help keep your hands cool while you dig around the cheesy top layer. They also keep the soup hot because they’re deep which reduces the surface area and minimizes cooling.

If you don’t have these particular bowls available, you can use any other type of bowl as long as it’s deep and oven safe, especially if you plan to place it under the broiler to melt the cheese. Here are some great affordable options from Amazon??

Buy it Here: French onion soup bowls

How to caramelize onions

The most time consuming (yet crucial) part of making vegetarian French onion soup is caramelizing the onions. It takes around 45 minutes to an hour to bring out their natural sweetness and create the signature incredible flavors of French onion soup.

My favorite onion for this soup is yellow onion. It’s nice and mild with a naturally occurring sweetness you want for caramelized onions.

To start, cut onions in half from the middle. Now is when I break out my trusty mandoline slicer, which makes this process so much faster. Just place the onion cut-side down on the mandoline and slice with a careful, controlled motion. Use the hand guard that’s included as you’re reaching the last part of the onion. Trust me on this: I once had a nasty cut from a mandoline for using it hastily and not using the hand guard. Ouch!

Buy it Here: Mandoline slicer

The trick to caramelizing onions is to let them fry for a good 5-8 minutes in between stirring to get those browned bits on the base of your pot. Then, with each stir, scrape the bottom of the pan to get those browned bits mixed through. The key is that your onions are soft, nicely browned and not burnt. It’s so important to watch the onions closely as they brown so they won’t burn. Medium low heat, frequent stirring and lots of patience is needed when caramelizing onions, but the payoff is worth it.

How to make vegetarian French onion soup

This vegetarian French onion soup is pretty easy to make, but it takes a bit of time due to the caramelization process, as described above.

First, slice 2 large yellow onions into thin slices (the mandoline is really handy for this). Next, heat up the olive oil in a large soup pot and start cooking the onions. Stir frequently to avoid burning, and continue cooking until the the onions start to soften and brown, around 20 minutes.

Buy it Here: Soup pots

Now, add the butter and continue cooking until they brown further, around 15 minutes more. Slow and steady is the name of the game here.

Now, add the salt and sugar and brown for 10 minutes more. The onions will be dark brown and soft, but not burnt. Add the garlic and cook until fragrant, around 1 minute.

Next, deglaze the pot with the red wine OR the extra broth. Scrape up the bits of onion stuck to the pan and combine well. Add the Worcestershire sauce, the vegetable broth, bay leaves, thyme and pepper and combine well. Simmer the soup, cover and cook for 20 minutes, stirring regularly.

While the soup is simmering, preheat the oven to 350° F. Brush the slices of bread with olive oil. Place in a baking sheet and toast for around 10 minutes, flipping over at the 5 minute mark to toast both sides.

Once the soup is ready, ladle it into oven proof bowls, place a slice of toasted bread on top of each bowl, and sprinkle with the shredded cheese. French onion soup is usually topped with Gruyere cheese, but I didn’t have any on hand so I used mozzarella.

Place all the bowls in a baking sheet and broil for a few minutes, until the cheese is melted and bubbling. Serve with some grated Parmesan cheese on top if desired.

If you don’t want to place all the bowls in the oven, you can also sprinkle the bread with the cheese and broil it, then place each slice of bread on top of a soup bowl, like I did below.

How do I make the French onion soup vegan?

You can easily turn this recipe into a vegan version by substituting the following ingredients:

Vegetarian French Onion Soup Recipe

Vegetarian French Onion Soup Recipe

Melissa E. Nieves, LND, RD, MPH
This savory soup is as flavorful as it is comforting. This easy recipe combines caramelized onions in a rich red wine infused broth and is topped with crusty french bread and melted mozzarella cheese. Bon Appetit!
Prep Time 15 minutes
Cook Time 1 hour
Total Time 1 hour 15 minutes
Course Soup
Cuisine French
Servings 6 servings


  • 2 large yellow onions, sliced thinly
  • 4 tbsp olive oil
  • 2 tbsp unsalted butter
  • 1 tsp sugar
  • 1 tsp salt
  • freshly ground black pepper, to taste
  • 4 fresh garlic cloves, minced
  • 8 cups vegetable broth
  • ½ cup red wine or use the same amount of vegetable broth
  • 1 ½ tsp Worcestershire sauce
  • 1 sprig of fresh thyme or ¼ tsp of dried thyme
  • 2 bay leaves
  • 6 slices of French bread
  • 1 cup shredded Gruyere or mozzarella cheese
  • grated Parmesan cheese optional


  • Heat olive oil over medium heat in a large soup pot. Add the sliced onions and cook until they start to soften, around 20 minutes, stirring regularly to avoid burning.
  • Once the onions start to caramelize, add the butter and continue to caramelize and brown them, stirring often, for around 15 minutes more.
  • Add the salt and sugar and continue cooking for around 10 minutes more, until onions are well browned, but not burnt. Add garlic and cook until fragrant, around 1 minute.
  • Add the wine (or vegetable broth if you don't want to use wine) and scrape the bits of onion from the pan, combining well.
  • Add the vegetable broth, Worcestershire sauce, thyme, black pepper and bay leaves. Simmer for around 20 minutes, covered.
  • While the soup is simmering, preheat the oven to 350°F. Brush the slices of bread with olive oil and place in a baking sheet. Toast in the oven for around 10 minutes, flipping the bread at the 5 minute mark.
  • Once the soup is done, serve in oven proof bowls, top with a toasted bread slice, and sprinkle the shredded cheese on top. Place the bowls in a baking sheet, and broil until cheese is melted and bubbling.
  • Serve immediately and top with a dash of grated Parmesan cheese, if desired.
Keyword Easy Recipe, French onion soup, Meatless Recipe, Vegetarian Recipe

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