Vegetarian French Onion Soup
This Vegetarian French Onion Soup features deeply caramelized onions simmered in rich mushroom broth, finished with melted Swiss and Gruyère cheese for a comforting, meat-free classic.
6 Servings
Ingredients
- 4 tablespoons unsalted butter
- 2 tablespoons avocado oil or other neutral oil
- 4 large yellow onions 8–10 cups, sliced ⅛-inch thick
- ½ cup dry white wine such as Sauvignon Blanc
- 2 tablespoons all-purpose flour
- 8 cups mushroom broth
- 3 sprigs fresh thyme
- 2 dried bay leaves
- 1½ teaspoons salt
- ½ teaspoon ground black pepper
- 1 tablespoon vegan Worcestershire sauce
- 2 teaspoons balsamic vinegar
- 1 French baguette sliced into 1-inch pieces
- 6 slices Swiss cheese about 6 ounces
- 1½ cups shredded Gruyère cheese about 6 ounces
Instructions
Caramelize the Onions
- In a 5-quart Dutch oven or large heavy-bottomed pot, melt the butter and oil over medium heat. Add the sliced onions and stir to evenly coat them with the fat. Cook for approximately 60 minutes, stirring every few minutes with a wooden spoon. The onions should gradually soften, reduce in volume, and develop a deep golden color. Scrape any brown bits from the bottom of the pot as they appear to prevent burning and to enhance flavor.
Deglaze the Pot
- Increase the heat to medium-high and pour in the white wine. Using a wooden spoon, scrape up any caramelized bits from the bottom and sides of the pot. Allow the wine to simmer for about 4 minutes, or until most of the liquid has evaporated.
Add the Flour
- Sprinkle the flour over the onions, stirring continuously until fully incorporated. Cook for 3–4 minutes to remove any raw flour taste, ensuring the mixture thickens slightly.
Add the Broth and Seasoning
- Pour in the mushroom broth, stirring to deglaze any remaining bits. Add the thyme, bay leaves, salt, and black pepper. Bring the soup to a gentle boil, then reduce the heat to medium-low and let it simmer uncovered for 15 minutes.
Finish the Soup
- Remove the thyme stems and bay leaves. Stir in the vegan Worcestershire sauce and balsamic vinegar. Adjust seasoning to taste.
Prepare for Broiling
- Preheat the oven broiler and position the rack on the top level. Line a baking sheet with aluminum foil and arrange six oven-safe bowls or crocks on the sheet.
Broil and Serve
- Ladle the soup evenly into the bowls, leaving about ½ inch of space at the top. Place 1–2 slices of baguette over each portion, followed by one slice of Swiss cheese and a generous sprinkle of shredded Gruyère. Carefully transfer the baking sheet to the oven and broil for 2–5 minutes, watching closely until the cheese is bubbling and golden brown.
- Remove from the oven and serve immediately while hot.
Notes
To make this Vegetarian French Onion Soup gluten-free, replace the all-purpose flour with a certified gluten-free flour blend or cornstarch (use 1 tablespoon). Substitute the baguette with a gluten-free loaf or sliced gluten-free bread. Double-check that your Worcestershire sauce is gluten-free, as some brands may contain malt vinegar derived from barley. The rest of the ingredients, including mushroom broth and cheese, are naturally gluten-free.