Vegetarian French Onion Soup with Mushrooms
This Mushroom French Onion Soup is a cozy, vegetarian twist on the classic. Caramelized onions and earthy mushrooms simmer in a rich, savory broth, then get topped with crusty bread and gooey melted cheese for the ultimate comfort food. Delicious on a chilly night or a dinner party starter.
Servings 4 people
Equipment
- Stockpot or Dutch oven
- Oven-safe soup crocks
- rimmed baking sheet
- Broiler
Ingredients
- 4 tablespoons olive oil or as needed to coat pot
- 2 medium sweet onions, sliced
- 1 shallot, sliced (optional)
- 2 large portobello mushroom caps, chopped into 1 ½-inch pieces
- 4 cups vegetable broth or mushroom broth
- 1 cup water
- 4 sprigs fresh rosemary
- Salt and pepper to taste
- 4 slices baguette or sliced bread of choice
- 4 slices vegetarian Gruyere cheese (see note)
- Fresh thyme leaves (optional)
Instructions
- Heat a heavy-bottomed pot or Dutch oven over medium heat and add the oil. Once the oil is hot, add the onions and a pinch of salt, then stir to coat. Cook the onions slowly, about 40 minutes, stirring every few minutes, or until they soften and turn golden brown. If the onions start to stick or darken too quickly, lower the heat and add a splash of water or broth to deglaze the pan. By the end, the onions should be deeply golden, jammy, and full of flavor.
- Stir in shallot and mushrooms and cook 5 minutes, or until the mushrooms turn dark brown.
- Pour in broth and water and stir in rosemary sprigs. Cover, bring to a boil, and then reduce heat to low and simmer 10 minutes, or until the flavors meld together. Season with salt and pepper to taste.
- Preheat the broiler and spread baguette slices on a rimmed baking sheet. Transfer baking sheet to the oven and toast bread 2 minutes on each side, or until golden brown. Remove from the oven and set aside. (Leave the broiler on because you will use it again.)
- Arrange 4 oven-safe soup crocks on the baking sheet. Divide the soup between the crocks. Place a piece of toasted baguette and slice of Gruyere cheese on top of each. Carefully return the baking sheet with the soup crocks to the oven and broil 2 minutes, or until the cheese is melted. Remove from the oven, garnish with fresh thyme leaves if desired, and allow to cool slightly before serving. (The soup crocks will be very hot. Serve on plates if desired.)
Notes
- Prep ahead: Caramelize onions and cook mushrooms in advance; store in the fridge for up to 3 days before finishing the soup.
- Refrigerate: Store cooked soup in an airtight container for up to 4 days.
- Freeze: Freeze soup (without bread/cheese topping) for up to 3 months.
- Before serving: Toast bread and melt cheese fresh to keep it crisp and gooey.
- Vegetarian: Gruyere cheese can be made with animal rennet, but some brands (such as Boar’s Head, at the time of article publishing) make vegetarian versions. If you can’t find suitable Gruyere cheese, substitute swiss, provolone, or mozzarella.
- Vegan and dairy-free: Omit cheese or substitute dairy-free cheese slices.
- Gluten-free variation: Omit bread or substitute sliced gluten-free bread.
- No oven-safe soup crocks? Melt the cheese on top of the soup in the microwave for about 20 seconds instead of broiling.