This classic vegan French onion soup is deeply savory and flavorful, thanks to patiently caramelized onions. It has a brothy texture and is topped with vegan cheese toasts. The cheese can be homemade, which I give instructions for, or store-bought: the choice is yours! French onion soup is a recipe that requires some time, but the steps are actually very straightforward—and the results are oh-so-worthwhile.

If you’ve been hoping to add a vegan or vegetarian French onion soup recipe to your repertoire, you’ve come to the right place!

This particular soup carries a lot of nostalgia for me. I’ve loved French onion soup since childhood.

When I was growing up, my mother and grandmother were both Francophiles when it came to food. One of my earliest restaurant memories is of eating French onion soup with them at a nice French eatery.

The deeply salty and savory broth was a delight. But it was that top layer of toasted bread and cheese that really won me over.

Today, a homemade version has become one of my favorite vegan soup recipes to make at home. I’d categorize it, along with classics like cozy vegan tortellini soup and creamy garlic chickpea soup, as a “comfort food” soup.

The recipe demands a little patience, but the reward is an exceptionally tasty, authentic, and supremely cozy dish.

What is French onion soup?

Many of us know and love French onion soup, but we may or may not know its story. I wasn’t familiar with the origins of the soup until I wrote about my vegan soup recipe that’s a tribute to it.

First, the facts: French onion soup is a soup made of onions that have been caramelized and simmered in some sort of broth. It’s served “gratinée,” or topped with toasted bread or croutons and cheese.

Now, a little history.

The quick history of a beloved dish

When I started to think about tackling French onion soup at home, I wondered whether it’s actually French, or rather an American recipe that’s inspired by characteristics of French cuisine.

As it turns out, French onion soup does in fact hail from France.

In the 19th century a famous Parisian food market, Les Halles, began serving French onion soup with gratinée bread and cheese on top. A trend caught on, and soon neighboring restaurants began to do the same.

According to writer Emily Monaco, French onion soup is not only a long-cherished hangover cure, but also a historically egalitarian dish.

For most of history, soups have been accessible to many, thanks to their generally inexpensive ingredients. When French onion soup became popular, it was quickly enjoyed by Parisians of all classes.

The soup began to make its way around the world later in the 19th century. It was dubbed “French onion soup” in Great Britain in the 1880s and first appeared in an American restaurant in 1861.

Variations of French onion soup

Most French onion soup recipes call for caramelizing onions with some type of fat, then simmering them in liquid.

That liquid can be broth alone, or it can be broth that’s thickened a bit with flour. Occasionally, I’ve seen variations that call for milk or cream.

The topping can be made of big, chunky croutons, which are topped with grated cheese, or small cheese toasts. And the bread for those toasts can be small slices of baguette or halves or quarters from a round boule.

Traditional cheese for French onion soup is Gruyére. However, this is a vegan soup recipe, which means that I’m offering you a dairy-free option!

You can use a homemade vegan cheese or commercial vegan cheese shreds. The homemade cheese will brown nicely in the broiler, while the commercial version will melt and stretch more easily.

Aside from the cheese substitution, this is a traditional take on the classic. My version of French onion soup is all about the onions, and that’s how I think it should be!

Caramelizing onions 101

At the end of the day, making a good pot of French onion soup comes down to one single, all-important process: caramelizing onions.

What does it mean to caramelize onions?

Caramelizing onions is the process of cooking onions over low(ish) heat for a long(ish) period of time.

The long, slow cooking process will allow the natural sugars in the onions to oxidize, or brown, taking on sweet, nutty flavors.

How is caramelization different from sautéing, or roasting?

If you’ve made oven-roasted onions or sautéed onions over high heat, then you’ve probably seen that the onions will almost always start to brown.

How is that browning different from caramelization?

The difference comes down to two factors: time and temperature.

Caramelized onions cook at a lower temperature for a longer period of time than do sautéed onions. As a result, their sugars oxidize more completely, and they take on a deeper, sweet flavor.

Sautéed or roasted onions will brown, but they generally retain more savory notes and sharpness than do caramelized onions.

How long does it take to caramelize onions?

Generally, caramelizing onions takes 40-60 minutes. A small batch of onions will likely take less time, whereas a large batch will take longer.

Each time I’ve made this vegan French onion soup, it’s taken me about 50 minutes to fully caramelize the onions.

Caramelized onions tips and tricks

It isn’t difficult to caramelize onions, but there are a few helpful tips to keep in mind.

Tip 1: Don’t raise your heat too high

When you’ve been stirring a pot of onions every few minutes for over half an hour, it’s tempting to crank the heat in order to cook the onions faster.

Try to resist this urge. Raising the heat too much will burn your onions, rather than caramelize them.

Tip 2: Choose a cooking vessel with a wide bottom

Since the caramelized onions in this recipe turn into vegan French onion soup, you’ll want to cook them in a large, heavy-bottomed pot.

I recommend a pot with a reasonably wide diameter, rather than a tall and narrow stockpot. More surface area gives more of the onions a chance to come into contact with heat and cook efficiently.

Tip 3: Stir every 10 (or so) minutes

There’s a delicate balance between stirring too often and too little while you’re caramelizing onions.

If you stir too much, you won’t actually give the onions a chance to spend time in contact with their heat source, browning beautifully.

If you stir too little, then the onions can start to burn and turn bitter, rather than caramelize and turn sweet savory.

I think stirring every 8-10 minutes is the right amount. It’s enough stirring to keep moving the onions around and making sure that they all come into contact with the bottom of the pot. Yet it’s also enough resting time to help them brown.

Can I caramelize onions in a non-stick pan?

As I was preparing to make this vegan French onion soup, I wondered whether my nonstick cookware would be an issue. Many caramelized onion recipes call for cast iron or stainless steel.

My verdict? Nonstick cookware can handle the job! The process will take a little longer to get started, but ultimately, time and heat will work their magic.

What type of onions should I use?

In a pinch, you can use pretty much any type of onion. I’ve caramelized red, white, yellow, and sweet onions.

However, Spanish onions are my favorite for caramelizing, followed by sweet onions. Yellow and white are fine for French onion soup as well.

The best type of broth

Traditional French onion soup can be made with beef, chicken, or vegetable broth. You can make this recipe with a plant-based version of any of those types of broth.

A beef-style broth will be most traditional. My favorite is the Born Simple Beef-Style Broth Concentrate, and Better than Bouillon is a good option as well.

You’ll need a fair amount of broth for the recipe—a whole eight cups.

Also keep in mind that the broth shouldn’t be ice cold. Use broth that is room temperature or prepared with hot water. If you’re reconstituting a bouillon cube or powder, you’ll be using warm liquid, anyway.

How to make vegan French onion soup

As you begin making this recipe, just remember: patience. This is recipe isn’t hard, but it does take time. Relax and enjoy the process.

Step 1: Slice your onions

Be prepared to take some time doing this, since the soup calls for about 3 pounds of onion!

To slice the onions for your vegan French onion soup, you’ll trim them and cut them in half lengthwise.

Then, use a slicer or chef’s knife to trim and thinly slice the onions. The slices should be about 3/16-1/4 inch / 4-6mm wide from root to stem.

Step 2: Caramelize your onions

This step is the big step.

You’ll begin by heating olive oil in a large, heavy-bottomed pot over medium high heat. Add the onions and salt.

At first, the onions will crowd the pot and fill it almost completely. As you stir them and coat them with oil, they’ll soften and reduce in size.

Cover the pot and begin the caramelization process, stirring the onions every 10 minutes. You can expect the caramelization step to take 40-60 minutes in total.

Step 3: Add garlic and white wine

Once the onions have browned to perfection, it’s time to season the onions and start to build the foundation of a soup.

Garlic and dry white wine are part of that process. You can omit the wine altogether if you like, but I don’t recommend skipping the garlic.

Step 4: Add a little flour

I think the soup takes on extra richness when you add just a small amount of flour to thicken it at this point.

Sprinkle two tablespoons of all-purpose flour (regular or gluten-free) lightly over the onions. Cook, stirring constantly, for a few minutes, or until the onions have thickened and the flour has cooked a little.

Add a cup of broth very slowly, stirring as you go. Then, add the remaining broth, two bay leaves, and a splash of vinegar to the pot.

Step 5: Simmer

Turn the heat to high and bring the soup to a simmer, then turn the heat back to low. Simmer the soup, covered, for 30 minutes. Remove the bay leaves, taste the soup, and adjust the salt and pepper as you like.

Step 6: Make cheese toast

Now it’s time to prepare those tasty gratinée cheese toasts for the soup.

I offer two cheese options for the toast. One is a nice batch of my melty vegan cashew mozzarella cheese.

This cheese is creamy and has a slightly stretchy consistency. It’s very versatile; I use it for topping baked lasagna or shells, for my vegan broccoli melts, and for pizza.

Once you make a batch of the cheese, you’ll spread it—be sure to do this while the cheese is hot—onto pre-toasted slices of bread.

I use the broiler to toast the bread. One or two minutes per side is enough; it will toast more when it returns to the broiler with cheese on top.

The bread you use can be from a round boule, or you can do triangles of sandwich-shaped bread. You can also use crosswise slices of baguette.

If you don’t have time to make your own vegan cheese, no problem. There are so many good, commercial vegan cheese shreds these days, which melt and stretch nicely.

My favorite are the mozzarella shreds from Good Planet Foods, but many other brands make this style of cheese.

In addition, you don’t have to use store-bought cheese shreds; you could also use slices of vegan mozzarella, American cheese, or Gouda-style cheese.

After you top your bread with cheese, you’ll transfer it to the broiler once again and give it 3-4 minutes, or until the cheese is toasty and melted.

Step 7: Top the soup with the cheese toast

At this point, you’ll divide the soup into bowls or ramekins and top each portion with the cheese toast.

If you use a smaller container, like a ramekin, the toast will cover all of the soup. If you use a bigger bowl, the cheese toast will probably be partially submerged into the soup.

At this point, it’s time to dip, dunk, and enjoy!

Make-ahead options

The vegan French onion soup is a wonderful option for vegan meal prep and make-ahead cooking.

The soup itself can be stored in an airtight container in the fridge for up to 1 week and frozen for up to 6 weeks. 

If you make the melty cashew mozzarella cheese, it can be stored in an airtight container in the fridge for up to four days. It will thicken in the fridge but is easy to reheat.

What to serve with vegan French onion soup

This soup is so hearty and warming that it could be a light meal unto itself.

However, I’m always a fan of serving any main dish with a vegetable side dish or two. I like to serve this recipe with my quick steamed green beans with Dijon vinaigrette and favorite butter lettuce side salad.

For a meal that’s all-classics, you could try pairing the soup with crispy broccoli Caesar salad. If you’d like something a little less traditional, you could serve it alongside a wintery spin on panzanella salad.

No matter how you choose to serve this time-honored, comforting soup, I hope you’ll love it.

My hope is that you’ll find many moments of coziness curled up with a bowl of this vegan French onion soup—and a crusty, broth-soaked slice of cheese toast.

Enjoy!

xo