Vegetarian French Onion Soup Recipe

Updated on December 10, 2019
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Linda explores food facts, folklore, and fabulous recipes, one ingredient at a time.


Years and years (decades?) ago, my husband and I discovered a restaurant near our office that, once a week, served French onion soup. I had never actually heard of French onion soup until I saw it on the menu (my mom was a good cook, but not very adventuresome).

To say that it was a "new taste sensation" is a gross understatement. Never before had I experienced a simple meal with so much intense flavor and texture in one tiny bowl—the richness of broth, the fragrance of herbs and onions, the creaminess of cheeses, and the crunch of toasted croutons.

And so over the years, with much trial and error (emphasis on the latter), I developed a recipe that I really liked. BUT, that original recipe included beef broth—not a favorite ingredient when someone you love (my younger daughter) is a vegetarian. So about 10 years ago, I began my quest to create that same wonderful, rich-tasting broth without the use of animals.

Here's how to do it:

The Key Components

The Onions, of Course

Why two types of onions? You might think that onions are all alike, that the difference between red, yellow, and white onions is only "skin deep." Not so. Each type of onion has its own characteristics of heat, bitterness, sweetness, and the ability to hold its shape or break down into creamy lusciousness. And don't we really want all of those things in our bowl of soup? Why settle for one flavor or texture when you can achieve a more complex experience with two onions? Here are the ones I chose:

Yellow Onions

These are considered the universal, all-purpose onion and make up about 75 percent of the world onion production. They are astringent yet sweet, and their sweetness intensifies with low, slow cooking. They can be round and fist-sized or flattened. Sweet varieties (Vidalia, Walla Walla, Maui) have a higher moisture content and so do not store as well.

White Onions

White onions have an all-white skin and flesh. They are slightly milder in flavor than the yellow onion and are a great substitute if you’re in need of an onion flavor, but don’t want it to be too powerful.

What about red onions? Yes they are pretty in salads, but their red flesh turns an odd grey color when slowly sauteed, so I'll save them for other purposes.

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Wine adds a layer of flavor to a vegetarian broth.A little tomato paste punches up the flavor of the broth, too.
Wine adds a layer of flavor to a vegetarian broth.
Wine adds a layer of flavor to a vegetarian broth. | Source
A little tomato paste punches up the flavor of the broth, too.
A little tomato paste punches up the flavor of the broth, too.

Umami Flavor Builders

Dry red wine

  • Rich red wines—especially those with high ripeness levels such as Shiraz—provide depth and a spicy-peppery note.

Tomato paste

  • Tomatoes in all their varied forms add savory qualities to foods, but tomato paste flavor is ultra-concentrated.

Canned, diced tomatoes

  • Here, diced tomatoes add texture as well as a tart, astringent note which compliments the sweetness of the onions.

Soy sauce

  • This fermented liquid—made from soybeans and wheat, barley, or rice—is almost synonymous with umami.


Choosing the Bread

This is not the place for your 9-grain, full-of-nuts-and-seeds loaf from the natural foods market. Nor would you want to waste your time with a simple slice of sandwich bread. French onion soup demands the sturdiness of a crusty artisanal loaf which will melt into the hot broth to create an almost fluffy custard-like mélange.

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The Cheeses

There are times to experiment, and this is not one of them. Don’t use any old cheese you have lying around—French onion soup demands Gruyere and Parmesan. The creamy luxurious way that Gruyere melts is almost sinful, and the umami blast from aged Parmesan is unparalleled.

Now, let's cook that French onion soup.

Cook Time

Prep time: 10 min
Cook time: 1 hour 15 min
Ready in: 1 hour 25 min
Yields: 4 to 6 servings


  • 3 tablespoons unsalted butter
  • 2 yellow onions, thinly sliced, about 1.25 pounds
  • 2 white onions, thinly sliced, about 1.25 pounds
  • 1 tsp. salt
  • 1/4 tsp. black pepper, ground
  • 1 cup dry red wine
  • 2 tablespoons tomato paste
  • 4 cups water
  • 1 cup canned diced tomatoes, drained (see Instruction #2 for how to use this ingredient)
  • 1 tsp. fresh rosemary, minced
  • 1/4 tsp. dried thyme leaves
  • 2 bay leaves
  • 1 tablespoon soy sauce
  • 1 day-old baguette, cut into 1/2-inch thick slices
  • 1/2 cup Parmesan, grated
  • 1/2 cup Gruyere, grated


  1. Sauté the onions in the butter in a large sauté pan or Dutch oven over medium-low heat, stirring frequently, until browned, about 45 minutes. (This first step requires a bit of patience. The onions need to caramelize low and slow to develop the rich, sweet flavor one associates with French onion soup. Hurry the process with high heat and you'll end up with bitter, burned onions. If you don't allow the onions to develop a deep golden color you'll end up with flabby, watery, and tasteless onions.)
  2. Increase heat to medium-high. Add salt and pepper, wine, and tomato paste. Cook until wine is almost evaporated (about 5 minutes). Add water, tomatoes, and herbs. Bring to a boil and then cover; reduce heat to simmer and cook about 20 minutes. Stir in soy sauce. Discard bay leaves. (NOTE: I prefer to leave the tomato pieces in our soup, but you may puree the tomatoes in a blender before adding them to the soup if you wish).
  3. OK, now you have the vegetarian stock. And you can use this for so many more things than French onion soup. So, keep this recipe in your back pocket (as my dad would have said) for future reference. But, if you want to proceed to turn this into ooey gooey cheesy goodness, continue with the instructions below.
  4. Preheat oven to 350 degrees F. Brush bread slices with olive oil and bake in the oven until edges are brown, about 5 minutes. Set aside.
  5. When ready to serve, whisk the 1/2 cup Parmesan into your hot broth. It’s important to whisk in the cheese at the last minute, or else the cheese will fall to the bottom of the pot and burn. Ladle the warm soup into heatproof bowls, and lay a slice of the baked bread over each bowl. Sprinkle a layer of Gruyere cheese over the bread, and place the crocks under the broiler until the cheese bubbles and browns.

What Makes This Recipe Work?

Typically when we think of French onion soup, we imagine caramelized onions slowly simmering in a rich beefy broth. What can we do to capture that savory taste without using animal protein? The key to the puzzle is understanding the science of taste.

There are five distinct tastes that the human tongue recognizes—sweet, sour, salty, bitter, and umami.

The first four you are probably familiar with:

  • sweet is a pleasurable sensation produced by sugars.
  • Sourness is the detection of acidity—the most common foods that contain the sour taste are citrus fruits, some melons, and some unripened fruits.
  • Saltiness is mostly from the presence of sodium.
  • A bitter taste is usually deemed unpleasant or disagreeable. Black coffee and unsweetened chocolate fall into this category.

And then there is umami. Umami is a Japanese word for "pleasant savory taste"—a meaty taste. There are several natural, non-meat foods that have a umami flavor—tomatoes, mushrooms, soy, potatoes, carrots, and Parmesan cheese.

So, if you create this soup for your family, you will be giving them an uber-umami taste without meat.

© 2013 Linda Lum


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