Vegan French Onion Soup

Made with mushroom broth, and omitting the cheese, this vegan French onion soup is more similar to older versions made across Europe than the perhaps more well-known modern dish popularised in the 1960s, especially in America. French onion soup may or may not be gratinéed – served with a cheese toast, versus plain toast – and this version is not.

While this soup is now typically made with beef broth, ancient versions would have used water and various other herbs and spices, and milk was common in the Renaissance period. We can confidently state that it’s a flexible soup, with a long history, that can be served in many ways.

This is a deeply savoury soup, with plenty of caramelised onion favour and an extra hit from the mushroom stock used. It uses simple ingredients but has a rather long cooking time due to the caramelisation process, so keep that in mind. It’s inexpensive and delicious but a little more time consuming.

If you have plenty of onions to use – we are growing about 400 this year, for example – try a potato onion galette, vegan mushroom pie, or vegan pasties, all made with caramelised onions as well.

Ingredients

Ingredient Notes and Substitutions

• Onions: any type of onion can be used, and I most often use plain white onions. Weigh them if possible, but if not, please note that medium onions are about tennis-ball sized.
• Bread: use whatever bread you like toasted. I use either spelt sourdough or baguette and a good gluten-free bread makes for an excellent GF option. Adding this crouton topping (sop) is an ancient holdover we don’t see too often, but is fantastic here.
• Oil: olive oil is recommended but you can use another cooking oil or vegan butter if preferred.
• White wine: dry white wine, no need for it to be pricey, is ideal. This can be replaced with an equal amount of broth if you don’t drink or have wine. I have also made this with red wine and liked that too.
• Cheese: to serve with a cheese toast, I recommend making the toast as directed, then melting vegan cheese on top in the oven before topping the soup. Vegan cheese often doesn’t melt as well when placed directly under the broiler.
• Flour: same as with the bread, use GF flour if needed, something like millet. You can also substitute one tablespoon of a starch, like cornstarch, in place of flour.
• Mushroom broth: the ideal substitute for beef broth in this recipe, it adds a similarly strong background flavour that pairs well with the onions. Substitute vegetable broth if preferred but note that the soup can taste bland this way.

Step by Step

Step 1: add the oil and sliced onions to a pot and cook over low heat.
Step 2: cook, stirring frequently, until the onions have caramelised, about one hour.
Step 3: add the garlic and cook for a couple minutes, then stir in the flour.
Step 4: deglaze with the wine and cook for a few minutes, uncovered.

Step 5: stir in the mushroom broth. Increase the heat to bring the soup to a simmer, then cook, covered, for 20 minutes.
Step 6: season to taste, add thyme if using, and serve with toast.

Recipe Notes

Be sure to use a large enough pot that the onions can be stirred frequently without falling over the top. I use the same cast iron pot as for baking bread and it works well (about 23cm across).

Consider the thyme to be optional and leave it out or replace with other herbs if preferred. It simply adds another layer to the soup, and pairs well with onions.

Your house will smell of onions after cooking this, and your hair and clothes might too. If it’s possible to open a window when cooking, do so, and you may want to plan to wash your hair not-too-long afterwards.

How to Store

Storage: to store, transfer cooled soup to a sealed container and don’t top with bread. Refrigerate for up to three days.

Freezing: ladle the cooled soup into freezer-safe airtight containers and freeze for up to three months (again, without the bread). Thaw in the refrigerator and reheat as usual.

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Expert Tips

• Take your time: don’t trust recipes that say you can caramelise onions in 20 minutes, they are lying through their teeth. Be patient to make a truly good soup.
• Season to taste: as always, soups should be tasted before serving and salt should be added to suit your preference.
• Add the toast immediately before serving: the bread will soften as it sits in the broth, so it should be toasted and served right away. Soggy bread can be very nice (e.g. zwieback) but perhaps not for this recipe.
• Do small servings: this is a rich soup and not one that should be served in a large bowl – think of it more as a side or starter, not a main, as it’s too much after a while.

More Vegan Soups

Vegan Borscht
Roasted Parsnip Soup
Cabbage Lentil Soup
Vegan Tomato Soup

If you make this Vegetarian French Onion Soup or any other vegetarian soup recipes on Occasionally Eggs, please take a moment to rate the recipe and leave a comment below. It’s such a help to others who want to try the recipe. For more OE, follow along on Instagram, Facebook, and Pinterest, purchase the Occasionally Eggs cookbook, or subscribe for new posts via email.