Vegetarian French Onion Soup

Vegetarian French Onion Soup is a classic French dish that consists of lots of onions, cheese, baguette, broth and fresh herbs. There’s nothing not to like about this dish: slow-cooked caramelized onions with french baguette and Gruyere cheese are some of my favorite things.

How to Caramelize Onions

The base for a good French Onion soup is caramelized onions. The slower-cooked and the deeper the caramelization, the better. You’ll want to cook down your onions for at least 40 minutes if you’re in a hurry, but it’s best to let them cook for around 2 hours on a low heat.

Make sure you slice your onions at least 1/8 of an inch thick- slicing them too thinly will make them more likely to burn.

Ensure that you are adding more than just butter to your pan when cooking them down. While everyone enjoys the flavor of butter (I know I do!) add in oil and then butter second. Adding a neutral oil will keep your onions and your butter from burning and will increase the smoke point.

Best Onions for French Onion Soup

Any onion with a lot of natural sugar will caramelize well. In the same vein, adding a bit of sugar to the pan as your onions are cooking down will help the natural caramelization process a bit – and a bit of sugar never hurt anyone.

  • Sweet Yellow Onions: These are my favorite when cooking down onions. They have the mildest flavor and have the highest sugar content, meaning they will caramelize the most readily.
  • Red Onions: Red onion had more zest than a yellow onion but also has a lot of natural sugar in it. It will cook down, but takes a bit more coaxing to caramelize as deeply as the yellow onion.

Whichever onions you choose, make sure to slice your onions about an eighth of an inch thick.

Yellow onions in the midway through caramelization.

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French Onion Soup is a classic french dish that is easy to make at home.
French Onion Soup is a classic french dish that is easy to make at home.

Ingredients for French Onion Soup

  • Large Sweet Yellow Onions: Sweet onions have a lot of natural sugars in them that caramelize beautifully when allowed to cook down.
  • Sugar: Adding white sugar to the onions while they are cooking down will help them caramelize. You don’t have to add it if you prefer not to, but trust me, it makes a difference.
  • Broth: French onion soup has a base of beef broth, but for this vegetarian recipe you can swap it out for Choose a low or no sodium beef broth so you can measure how much salt to add to your soup.
  • Thyme: Adding a fresh herb bouquet is always something I encourage, but if you’re not in a position where fresh herbs are attainable, dried will do.
  • Gruyere cheese: French onion soup is traditionally made with Gruyere cheese. Something you’ll notice about this cheese when you pick it up at your local supermarket is how smelly it is. After the cheese is broiled on top of the crouton and soup, it just melts into the dish. You can replace the cheese with a different kind, just ask your local cheesemonger.
  • Baguette: A toasty baguette is what makes the crouton that floats in the soup that is topped with Gruyere cheese.
  • Wine: A dry white wine will add a depth of flavor to the soup. Add it in after the onions have caramelized but before adding the beef broth.

How to Make French Onion Soup

Something that’s great about French Onion Soup is how easy it is to make. You basically chop up a bunch of onions and let them cook down until they are caramelized until deeply golden brown in a beef broth.

The first step in this hearty onion dish is to caramelize the onions. You’ll want to add your chopped onions, butter, salt and sugar to a large stockpot over medium heat. The added sugar will help the onions caramelize with their natural sugars. The biggest tip I can give you with this part of the soup is to resist the urge to move the onions around too much. Pushing the onions around too much will disturb the natural caramelization process of the onions. Only stir the onions once every four to five minutes to ensure that they are not burning and to make sure that the onions are cooking evenly.

After your onions are richly caramelized, which should take around 30 minutes, deglaze the pan by adding the beef broth. Reduce for about 20 minutes and add in your fresh herbs and add in your wine.

While your soup is reducing, set your oven to broil and add cheese on top of your baguette. When your oven is ready, place your baguette slices in the oven and let broil until the cheese is bubbling on top- about 5 minutes.

Taste your soup and adjust the seasonings to your liking- what does it need? More salt? A bit more sugar? Adjust before serving.

French Onion Soup

5.0 from 1 vote
Recipe by Sarah
Course: Appetizers, Easy Recipes, EntreesCuisine: FrenchDifficulty: Easy


Prep time


Cooking time






  • 4 yellow onions

  • 6 cups broth

  • 1.5 cups dry white wine

  • 4 tbsp butter

  • 2 tbsp oil

  • 1 tsp sugar

  • 4 sprigs thyme

  • 1 tsp salt

  • 1 tsp pepper

  • baguette

  • 1 cup Gruyere cheese


  • Prep your ingredients. Slice all your onions and measure out your butter and oil.
  • Caramelize the onions. Over medium heat, add the butter and oil to your dutch oven and add your onions, salt, pepper and sugar. Coat the onions and let them sweat down and caramelize for about 40 minutes. Resist the urge to push the onions around too much, which will disturb the caramelizing process.
  • Add the liquids. Add in your broth and reduce for about 15 minutes and then add in your wine. Add your thyme and bring to a simmer and season to taste.
  • Make your croutons. Set your oven to broil to make your crouton toppers. Add your Gruyere on top of slices of baguette and place in the broiler for about five minutes. Remove when the cheese is golden brown and bubbly.
  • Assemble. Place your soup in a bowl and add your cheesy croutons on top. Serve immediately and enjoy. Careful, it will be hot!

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