Vegetarian French Onion Soup

5 from 4 votes

Classic French onion soup with a vegetarian twist! This easy recipe is made with caramelized onions, toasted bread, and lots of melty cheese!

Prep Time15

Cook Time1 15

Course: Appetizer, Soup

Cuisine: French

Diet: Vegetarian

Servings:

Calories: 620kcal

Author: Leigh Anderson

Ingredients

Vegetarian French Onion Soup

6 c mushroom stock homemade or store-bought
6 medium yellow onions peeled, halved, and thinly sliced
1/4 c butter
1 tbsp flour
1/2 c dry sherry
4 sprigs thyme
2 tbsp Worcestershire sauce make sure to buy vegetarian, see note
1 tbsp vinegar sherry, white wine, champagne, or red wine
8 slices swiss or gruyére cheese
1 baguette
salt and pepper

Homemade Mushroom Stock

1 tbsp olive oil
1 medium yellow onion peeled and halved
2 carrots peeled, stem removed
1 head garlic
8 oz button mushrooms
1 oz dried shiitake mushroom
3 sprigs thyme
1 small handful parsley
1 tbsp black peppercorns
8 c cold water
salt

Instructions

Soup

Melt the butter in a large soup pot over medium-high heat, then add in the sliced onions and a generous pinch of salt. Cook on medium-high heat for about 10 minutes, stirring occasionally so that the onion does not burn. Reduce heat to medium-low to caramelize gradually. This will take some time, about 30 minutes.
When the onions have caramelized to a golden brown color, add in the flour and cook, stirring, for 1 minute. Next, deglaze with the dry sherry. Continue stirring until most of the sherry is evaporated then add the thyme, Worcestershire, vinegar, and mushroom stock. Simmer on low for 20-30 minutes. Season to taste with salt and pepper.
Preheat the oven to 400°F. While the soup is simmering, slice the baguette into 1/4-inch thick pieces and arrange them in a single layer on a baking sheet. Bake for 5 minutes, until the bread is toasted and golden around the edges. Remove and set aside.
Switch the oven to broil. Ladle the soup into oven-safe bowls. Add 1-2 slices of toasted baguette to each and top with two slices of cheese. Place each soup bowl on a baking sheet and transfer to the oven, broil until bubbly and golden brown, 2 to 3 minutes. Serve immediately!

Homemade Mushroom Stock

Heat the olive oil in a large stock put over medium-high heat. Add the onion, mushroom, and carrot to the pot. Sauté 5-10 minutes, stirring frequently.
Add the remaining ingredients as well as a generous pinch of salt then cover with 8 cups of cold water. Bring the stock to a boil, then turn the heat to low and simmer, uncovered, for 1 hour. Pour the stock through a strainer, pressing as much liquid as you can from the vegetables, then discard them.

Notes

What is vegan/vegetarian Worcestershire?

Worcestershire sauce traditionally contains anchovies. The icon brown paper-wrapped bottle of Lea & Perrins is a no-go for vegetarians. Instead grab the vegan version from Annie's.

What can I substitute for sherry?

Any dry white or red wine can be used in place of sherry in this recipe. If you prefer to not cook with alcohol you can simply omit it.

What to do if you don't have oven-proof bowls

If you don't have oven-proof bowls you can skip the broiling by melting the cheese on top of the toast in the oven and then place them on top of the soup just before serving.

Do you have to make your own mushroom stock for this recipe?

Nope! You can use boxed mushroom or vegetable stock.

Is cheese vegetarian?

Not all cheese is vegetarian-friendly! Many kinds of cheese are made with "rennet" which is an enzyme that comes from the stomachs of cows. Luckily, there are a few brands that make "vegetarian-safe" cheeses free from rennet. Organic Valley, Horizon, Applegate, and Tillamook all offer vegetarian cheeses and are readily available at most supermarkets.

Nutrition