Instant Pot French Onion Soup (Vegetarian)

Instant Pot French Onion Soup is a restaurant-quality vegetarian soup, with a savory and sweet flavor instead of the bitter taste present in the classic soup. It is loaded with caramelized onions and topped with toasted bread and gooey, melted cheese. So delish!

 

French Onion Soup Recipe

Classic French onion soup calls for caramelized yellow onions, beef broth, dry white wine, toasted bread, and a broiled melting cheese such as gruyere.

Of course, there are variations of the soup, depending on the region. The Gratinée Lyonnaise version uses chicken stock, for example.

The thing is, onion soups date as far back as Roman times. They were seen as food for poor people, since onions are plentiful and cheap.

But the most popular modern version originated in Paris, France in the 18th century, using beef broth and caramelized onions for deep flavor.

It’s served either as a first course or as a meal in itself.

Ingredients and Substitutions for Vegetarian French Onion Soup

• Onions: Use sweet yellow onions or, if you prefer, red onions instead.
• Olive oil: Our version calls for olive oil but you can use unsalted butter instead.
• Brown sugar: This will speed up the caramelization process, giving the onions a sweeter flavor. If you are on a keto diet, use baking soda instead (not baking powder).
• Aromatics: We used garlic, bay leaf,  and fresh thyme, but you can use dry herbs instead.
• Liquids: Worcestershire sauce, vegetable broth (for a non-vegetarian version, use either beef or chicken broth), and dry white wine (you may replace with red onion for a more robust flavor).
• Seasonings: Salt and freshly ground black pepper.
• Bread: Toasted French bread, baguette, or homemade croutons. If on a keto diet, use keto cauliflower bread, toasted.
• Cheese: Use melting cheeses such a Swiss or Gruyere cheese. Other options: mozzarella, white cheddar, Asiago, and/or gouda.
• All-purpose flour: We use it as a thickener, but you can replace it with cornstarch (add twice as much white flour as cornstarch). If you are on a low carb diet, use half as much xanthan gum as flour)

How to Make Instant Pot French Onion Soup

This vegetarian French onion soup is made in the Instant Pot instead of on the stovetop because it is quicker to prepare. The process is quite simple! Just follow these steps below:

1. Caramelize the onions: Press the Sauté button of your Instant Pot or pressure cooker. Let it heat for 2-3 minutes and add olive oil. Add sliced onions and stir in brown sugar. Sauté, stirring every now and then in order to keep it from burning, for about 15-20 minutes or until onions are golden brown or caramelized. (SEE PIC. 1) NOTE: Because the pot is tall but not so wide, you may have to half the recipe, or cook half of the onions on the stovetop. If cooking the whole 4 pounds of sliced onions in the Instant Pot, it may take a few minutes more to caramelize. Make sure to stir them more often.

2. Add aromatics, seasonings, and liquids: Next, add minced garlic and cook for 1 minute. Then, combine Worcestershire sauce and wine. Let the wine evaporate a little and stir in salt, pepper, broth, thyme, and bay leaf. (SEE PIC. 2)
3. Pressure Cook: Lock the lid, turn the valve to sealing, and cook on high pressure for 15-20 minutes. Let the pressure release naturally. (SEE PIC. 3)
4. Thicken the soup: Open the pot and stir in a mixture of flour dissolved in water. Press the sauté button and cook, stirring constantly, for about 8 minutes or until the soup thickens. Can you skip the thickening process? YES! Transfer the soup to bowls and top with toasted bread and cheese. (SEE PIC. 4)

5. Broil: Place the oven-safe bowl onto a baking sheet and transfer to the top oven rack (must be about 6 inches from the heat source) and broil for 3-5 minutes, or until the cheese is golden brown, bubbly, and melted. Watch carefully in order for the cheese to not get burnt. (SEE PICS. 5 & 6)

Do I have to caramelize the onions for making French Onion Soup?

If you are in a hurry, you can skip the caramelization process but it will alter the flavor of the soup.

Authentic or traditional French onion soup recipes call for caramelizing the onions because it adds depth of flavor to the soup.

How to Caramelize Onions

If caramelizing the onions on the stovetop, use a heavy-bottom pan and sauté the onions in butter or oil over medium-high heat for about 30 minutes, or until caramelized. Make sure to stir every now and then to prevent burning.

Doing on the Instant Pot is easier. Just use the sauté function, add butter or oil, and cook the onion, stirring occasionally.

In either case, add a small amount of brown sugar to speed up the process. It takes around 15-20 minutes to caramelize onions in the Instant Pot. Some people use baking soda instead (not baking powder).

When you add either sugar or baking soda during the cooking process, you change the pH, which increases the Maillard reaction, causing the onions to brown more quickly. Because baking soda can alter the taste of the onions a lot, some recommend using only ⅛ to ¼ teaspoon per pound of onions.

As noted earlier, the browning or caramelization of onions is a Maillard reaction. As onions cook, they release their moisture and soften. Sugars are released, and as they heat up, they start to brown.

The same reaction happens when you sear a steak or when you cook a roast, and it gets brown on the outside.

How to Toast the Bread

In order to not turn soggy, a stale or hard-crusted bread such as our no yeast bread is ideal for topping the soup.

1. To toast the bread, preheat the oven to 400°F (204° C).
2. While the soup is cooking in the pressure cooker, slice a French bread or baguette into 1-inch thick pieces and arrange the slices in a single layer on a baking sheet lined with foil. Brush olive oil on top if you want. 
3. Bake for 6-8 minutes, or until the bread is toasted and golden brown. Set aside.

If you prefer, use store-bought or homemade croutons. They are easier to spoon while eating the onion soup.

Onion Soup Variations

You can customize this soup by adopting a few shortcuts or tweaks to the recipe. Feel free to:

• Skip the broiling process:  If you don’t have oven-safe bowls for this recipe, you can top the soup with croutons, sprinkle the cheese on top, and microwave in order to melt the cheese, making an easy French onion soup.
• Use store-bought croutons instead of toasting bread, saving some time. 
• Use dried herbs: If you don’t have fresh herbs, use a third as much dried herbs as fresh herbs.
• Make a vegan French onion soup: Use vegan butter (or olive oil), vegetable stock, vegan brown sugar and Worcestershire, and vegan cheese.
• Make it keto and gluten-free: Use xanthan gum instead of flour, replace brown sugar with baking soda, and pick keto bread.
• For slow cooker French onion soup: You can caramelize the onions in a pot on the stovetop or skip this process and dump all the ingredients in the crockpot except the flour, bread, and cheese. Just cook on low for 8-10 hours, and thicken the soup at the end. Then ladle the soup into bowls, top with bread and cheese, and broil.

How to store leftovers

• To refrigerate: This is one of those easy freezer meals! Allow the leftovers to fully cool and store in an airtight container in the fridge for up to 5 days.
• To freeze: After the leftovers cool, store the soup either in a freezer bag or container, and freeze (without the bread and cheese) for up to 3 months.
• Thaw and reheat: Thaw it in the fridge overnight and reheat our vegetarian French onion soup in a pot on the stovetop. Then pour into ceramic bowls. Top with toasted bread and cheese, and broil following our recipe.

Other soup recipes to try

• Instant Pot potato leek soup (vegan)
• Instant Pot Weight Watchers chicken tortilla soup
• Norwegian fish soup
• Cabbage soup diet recipe (vegetarian)
• Panera Autumn squash soup (vegetarian)
• Creamy pumpkin soup (vegan)
• Provençal vegetable soup with pistou

PIN & ENJOY!

 

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