Cheesy Gratinéed Vegetarian French Onion Soup

Warm, cheesy, and packed with rich flavor, this Vegetarian French Onion soup recipe is a modified version of the classic French dish. We like to serve this gratinée style at our house, meaning we broil the dish in the oven topped with the croutons and cheese.


Cold Weather Saviour

Who doesn’t love a warm bowl of soup on a chilly day? Soup is easily one of my top 5 favorite meals, ESPECIALLY when it is topped with a crunchy crouton, and melty cheese.

This soup is made vegetarian by swapping out the traditional beef bone broth for a vegetable based broth. This can be homemade, or if you’re feeling lazy you can definitely use a store-bought option. This is a judgment free zone!

How to make the best french onion soup

I firmly believe that making a good French Onion soup can be boiled down (ha, get it?) to taking your time, and using good quality ingredients. In the kitchen, patience is always rewarded.

I understand that extra time is hard to come by these days, but setting aside a few extra moments for the onions during the caramelization process is absolutely essential. The caramelization of the onions darkens the color and makes them nice and “jammy”. The darker they become, the sweeter the flavor. This should be done “low and slow”, and takes about 45 minutes to an hour.

Having patience during this process will make a world of difference by allowing those onions to break down their large sugar molecules into smaller simple ones. These smaller sugar molecules have a sweeter presence on our palate, and will round out the profile of the soup.

Which Cheese is best For Topping The Soup?

Gruyère is the traditional choice for this soup, and for good reason. Gruyère is a firm cheese with a rich, creamy and nutty taste. It is absolutely fabulous for melting, which is why it is one of two main cheeses (Emmental being the other) used in the preparation of traditional Swiss fondue.

It is important to note that although most cheese is vegetarian, Gruyère is often made with rennet, therefore rendering it not suitable for those following a meat-free diet. If this concerns you, there are some vegetarian friendly alternatives. Boars Head makes a product named Blanc Grue which mimics the flavor profile of traditional Swiss Gruyère. This can be a lovely substitute. If you seeking vegan products, Violife has a range of delicious options.

I highly recommend speaking to your local deli clerk or leaving a comment down below for more recommendations.

More On Gruyère

In 2019, I got the opportunity to visit Gruyères with my mother. Switzerland was a dream, but going to Gruyères felt like stepping into the past. It was such a quaint little town with lovely locals, and a rich history. I can’t help but reminisce whenever I use this ingredient.

This cheese embodies tradition, and is a product of care and hard work. The level of care is demonstrated during the production process of the milk where the pasture-fed alpine cows are free to roam streams and hillsides.

Did you know?

Gruyères is the only region in the world that can produce the cheese with the same name. It is protected by an “AOP”.

An “AOP” (appellation d’origine protégée), designates a controlled and protected origin for a product. An AOP/AOC certifies that a product is produced following strict traditional methods, and quality control standards. Another good example of this is Champagne, which can only be produced in the Champagne region of France. Any sparkling wine produced elsewhere cannot be labelled as “Champagne”. This is in place to protect a name, and certifies quality, craft, and tradition.


Final Thoughts

French Onion soup always feels like a special indulgence whenever we make it. It is quite simple, with minimal ingredients and can be completed from start to finish in about an hour & a half. This soup is best enjoyed hot and fresh out of the oven after broiling the cheese. If there is any leftover soup, it can be stored in the refrigerator for about 3 days in a jar. Enjoy, and please let me know if you have tried this recipe! I’m always open to feedback and I adore seeing you experiment in the kitchen! xo


Vegetarian French Onion Soup

Prep Time15 minutes
Cook Time1 hour
Total Time1 hour 15 minutes
Course: Main Course, Soup
Cuisine: French, vegetarian
Keyword: french onion soup, soup, vegetarian
Servings: 4 servings

Ingredients

Soup

  • 2 tablespoons olive oil
  • 1 tablespoon butter
  • 6 large yellow onions sliced thinly from root to stem lengthwise
  • 1 teaspoon organic granulated sugar
  • ½ teaspoon dried thyme leaves
  • 6 cloves garlic minced
  • 1 teaspoon Kosher salt
  • ½ cup dry white wine
  • 2 L vegetable stock can be homemade or purchased
  • 1 bay leaf

Crouton and Toppings

  • 1 Demi French Baguette sliced into 1 inch thick pieces, about 10 slices
  • 1 tablespoon olive oil
  • 8 oz. Gruyère cheese grated, about 1 ½ cups
  • Freshly cracked black pepper to taste

Instructions

  • 1. In a large heavy-bottomed pot over medium heat, add the olive oil and butter. Add the sliced onions, and sauté until soft and translucent, about 10 minutes. Sprinkle the onions with the sugar, and dried thyme leaves. Reduce the heat, and continue cooking the onions, stirring frequently, until they are caramelized. This will take about 30-45 minutes.
  • 2. Once the onions are caramelized, add the garlic, and sauté until fragrant. Deglaze the bottom of the pot by adding the white wine, stirring and scraping the bottom.
  • 4. Add the vegetable stock, the bay leaf, and Kosher salt. Bring to a boil, then cover and reduce heat to a simmer, allowing the soup to finish up.
  • 5. Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper, and arrange the sliced baguette onto the sheet. Drizzle and brush the olive oil onto each slice. Bake for 5 minutes, or until lightly toasted.
  • 6. To serve, remove the bay leaf, ladle the soup into a broiler-safe dish and top with the toasted baguette and cheese. Broil for 2-3 minutes, or until the cheese is toasted, and gooey.

Notes

To make this soup vegan friendly, I recommend simply swapping the butter and cheese topping to a vegan friendly version. Violife makes a delicious pre-shredded mozzarella style cheese, and Miyoko’s Creamery makes a fantastic butter substitute. 
When in a hurry, I use “No Salt Added” Organic vegetable stock. I prefer a reduced sodium stock because some store-bought options can be heavily salted.

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