French Onion Soup is by far the most requested soup for dinner parties with our friends and family. My vegetarian take on this rich and indulgent dish boasts flavors of caramelized onions, toasty buttered croutons, sweet thyme, and of course, melted gooey cheese.

French onion soup in a white bowl with a some soup in a spoon

Traditional recipes can be time-consuming; but with the help of the Instant Pot, this French onion soup is ready in under an hour. With the same luxurious flavors and sweetness from caramelized onions, topped with toasty croutons and cheese broiled to golden perfection!

Instant Pot Sauté function is perfect to cook and brown the onions. The pressure cooking option seals all the flavors inside making the onions melt-in-your-mouth creamy. Infused with bay leaf and fresh thyme, this vegetarian French onions soup is a must-try recipe.

Tips

I like to use large yellow onions in this soup because they lend to a mellow, sweet taste with the perfect brightness in the end. You can also add a mix of onions. Make sure to thinly slice them with a mandolin,
Traditionally made with beef broth, I love making a vegetarian version of this classic French onion soup with the Better Than Bouillon seasoned vegetable base. It increases the flavor intensity and also helps to get that perfect brown color to the soup.
Use good quality dry white wine such as Pinot Grigio, Sauvignon Blanc, or Chardonnay. The broth along with the wine adds the perfect richness and acidity to the soup. If you are not a big wine drinker buy the smaller single-serve wine bottles.
The Worcestershire sauce adds savory, umami flavors to the soup and is also available as a Vegan option in most grocery stores.
Although dried thyme can be used in a pinch, I recommend using fresh thyme for more bold flavors and also adding some as a garnish while serving
Use fresh, good-quality cheese. I like to top the soup with a handful of shredded Gruyere cheese and sliced Swiss cheese
Finish off with a sprinkle of spicy cayenne pepper to perfectly balances the flavors of this classic bistro soup

French onion soup in a white bowl with a spoon on the side

Process

Turn the Instant Pot on Sauté(more) mode and heat butter and oil.
Add onions, ½ teaspoon salt, ¼ teaspoon sugar and cook for 20-25 minutes stirring every 5 mins until onions turn golden brown but not burnt. Glass lid can be used during Saute process.
After 20 minutes the onions should be golden brown and the bottom of the pot will start to brown (Photos 1 - 4).

steps one through four of making french onion soup

Press Cancel. Add wine and deglaze the pot removing all browning from the pot. Cook for 2-3 minutes as the wine evaporates.
Add bay leaf, thyme, remaining salt, pepper, Worcestershire sauce, and broth.
Secure the lid with Pressure Release to Sealing. Cook on Manual/Pressure Cook (Hi) for 6 minutes followed by Quick Release.
Open the Instant Pot, remove the bay leaf and discard. Mix all-purpose flour in the remaining broth and slowly stir in the soup. Set Instant Pot to Sauté mode and cook for 5 minutes as the soup thickens (Photos 5 - 8)

steps five through eight of making french onion soup

Next, make some homemade croutons. Slice a crusty baguette into thick bite-sized pieces. Brush them with some butter for more rich flavors and then toast them in the oven (photos 9 - 10)

steps nine and ten showing how to make croutons

Serving

Ladle the soup in oven-safe bowls. Place the bowls in a baking tray, this makes them really easy to take in and out of the oven, especially when serving to multiple people at once.
Line the toasted croutons on top of the soup.
Next spread a handful of shredded Gruyere cheese and top with sliced Swiss cheese. Sprinkle spicy cayenne pepper to perfectly balances the flavors.
Place the tray in the preheated oven and broiled just until the cheese melts and starts to brown. (photos 11 - 14)

steps eleven through fourteen showing how to serve french onion soup

Be careful when you take out the tray and serve. Enjoy hot!

Storing

Any leftover soup can be refrigerated for up to 5 days or even frozen. Make sure to refrigerate or freeze the cheeses and croutons separately. Thaw the soup overnight and microwave. Then assemble the soup in ovenproof bowls and broil as per the recipe.

close up photo of a bowl and spoon with french onion soup

Meal Prep

This french onion soup is perfect for meal prepping. It is a fridge and freezer-friendly recipe:

Refrigerate the pressure-cooked soup 1 to 2 days ahead. Reheat and assemble the soup bowls with croutons and cheese when ready to serve.
You can also freeze the pressure-cooked soup for up to 2 months. I would recommend freezing in individual portions so it is easy to thaw and reheat.

Did you enjoy this delicious soup? Here are some more of my favorite Instant Pot Soups:

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Author: Archana

Hey there! I am a techie turned recipe developer, cooking instructor, and food blogger. I love food and enjoy developing easy and healthy recipes for busy lifestyles. I live in New Jersey with my husband and two sons.

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