Vegetarian French Onion Soup is one of our favourite healthy soups to enjoy during the cold Fall and Winter months.
Our homemade Vegetarian French Onion Soup recipe is quick and easy to make, ready to serve in under 2 hours.
Spoon through a bowl of our meat-free French Onion Soup featuring flavourful garlic, onions, sherry, thyme, mushroom broth, Worcestershire sauce and gruyere cheese.
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What Is French Onion Soup?
French onion soup has been a staple of French cuisine since at least the 18th century.
Originally a humble, rustic meal, it was popular among French labourers because it was made with simple, inexpensive ingredients, mainly onions, butter, and broth. Onions were slow-cooked to bring out their natural sweetness, creating a rich, comforting flavour despite the simplicity of the dish.
The addition of bread and melted cheese, which became standard in the 19th century, elevated the soup from a modest staple to the beloved, indulgent version we recognize today.
Traditionally, it was made with beef stock, which added depth to the caramelized onions, but vegetarian and mushroom-based variations have become popular in modern cuisine, making the dish accessible to a wider audience.
With a little patience for caramelizing the onions and the right combination of mushroom broth, sherry, and seasonings, this soup delivers a deep, satisfying flavour. Topped with slices of toasted baguette and melted Gruyere, it’s elegant enough for dinner parties but comforting enough for a cozy night in.
Why You’ll Love This Recipe
- Customizable: Use vegan cheese or bread options for a fully plant-based version
- Vegetarian-friendly: Full of flavour without using beef stock
- Rich and comforting: Caramelized onions add natural sweetness and depth
- Perfect for entertaining: Individually baked, cheesy bowls make a stunning presentation
How To Make French Onion Soup
- Caramelize the onions: Heat butter in a large pot or Dutch oven over medium heat. Add garlic, sliced onions, and salt. Cook for 30 minutes, stirring every few minutes to prevent burning.
- Slow-cook for sweetness: Sprinkle in sugar, lower the heat, and cover the pot. Continue cooking for approximately 50 minutes until the onions are golden brown and deeply caramelized.
- Add flour: Remove the lid and stir in the flour. Cook for another 5 minutes to eliminate the raw flour taste.
- Simmer the soup: Add mushroom broth, Worcestershire sauce, sherry, thyme, and cracked black pepper. Simmer gently for 20 minutes to let flavors meld.
- Prepare the bread: Slice the baguette into 1/2-inch rounds and toast until crunchy.
- Assemble the bowls: Preheat oven to 350°F. Line a baking sheet with aluminum foil. Place 4–6 ovenproof bowls on the sheet and ladle soup into each bowl. Stir in 3 tbsp shredded Gruyere per bowl. Top with 1–2 slices of toasted baguette and sprinkle 1/4 cup more Gruyere on top.
- Bake and broil: Bake in the oven for 10 minutes until the cheese is melted and bubbling. Broil for 1–2 minutes to achieve a golden, bubbly crust—watch closely so the bread doesn’t burn. Serve immediately.
French Onion Soup Recipe Tips
This healthy homemade vegetarian soup is quick and easy to make at home. We’ve included a few tips for first time soup makers!
- Use a large cast iron dutch oven with a high rim to reduce splatter when cooking.
- We suggest using a high quality rubber spatula spoon when making soup so you can easily stir, scrape down the side of the pot and sip to check if it needs to be seasoned further with more salt before spooning into bowls.
- You’ll save yourself plenty of tears and time by slicing all of the onions in a food processor. If you’re slicing onions by hand, use our funny trick to avoid crying at your cutting board. Simply strap on your swimming goggles and chop away!
- We’ve used mushroom stock in this recipe because we love its umami flavour, which mimics beef broth. You can also use vegetable broth.
- Presentation tip: Serve in individual ovenproof bowls for a dramatic and cozy presentation
- Be patient with the onions: Caramelizing slowly is key to developing rich flavour
- Use high-quality mushroom broth: Adds a savoury depth similar to traditional beef stock
- Stir often during caramelization: Prevents burning and ensures even cooking
- Cheese alternatives: If you can’t find Gruyere, Emmental or mozzarella works well as they easily melt.
What to Serve with Vegetarian French Onion Soup
This soup is rich, hearty, and deeply flavorful, so simple sides complement it best. Consider pairing with:
- A glass of white wine, such as Chardonnay or Sauvignon Blanc, to balance the richness
- A crisp green salad with vinaigrette for contrast
- Roasted or steamed vegetables on the side
- Crusty bread or extra baguette slices to soak up the broth
Storing Soup
If you have leftover Vegetarian French Onion Soup you can store the soup base in the fridge in an airtight container for up to a week. To reheat simply zap it in the microwave or simmer in a small saucepan on the stove.
Do not store the soup in the fridge or freezer with baguette slices and shredded cheeses. Store the leftover cheese and bread separately in ziplock bags and assemble in bowls and gratin in the oven when ready to eat.
We love doubling our soup recipes so can store leftovers in the freezer and save time on cooking in the kitchen. We suggest storing leftover soup in Pyrex freezer safe containers that have a snug lid so there’s not spilling. My mother often uses old glass pasta sauce jars to store soup in the freezer.
Be sure to let your soup reach room temperature before storing it in the freezer. If you add a hot jar of soup to a cold freezer it will significantly reduce the interior temperature and potentially spoil your food.
You May Also Enjoy These French Recipes…
- French Mashed Potato Fritters
- Creamy French Poulet a la Creme Casserole
- French Orange & Fennel Braised Provencal Chicken
- Roasted Garlic Gruyere French Tomato Tart
- Brandy Caramelized Onion French Burger
- Tartiflette Reblochon
- Lillet Blanc Spritz Cocktail
- Grand Marnier Sidecar Cocktail
- French Blackcurrant Creme de Cassis Cocktail
- Chambord French Martini
Easy Vegetarian French Onion Soup
Equipment
- Dutch Oven
- oven
- French knife
- measuring spoons
- measuring cups
- Wooden spoon
- cheese grater
Ingredients
- 5 tbsp Butter
- 2 Garlic cloves minced
- 5 Large sweet onions sliced
- 1 tsp Kosher salt
- 1 tsp White sugar
- 2 tbsp All purpose flour
- 6 cups Mushroom broth
- 1 tbsp Vegan Worcestershire sauce
- 1/2 cup Sherry
- 1/4 tsp Fresh thyme
- 1/4 tsp Ground black pepper
- 1 French Baguette sliced
- 14 oz Gruyere cheese shredded
Instructions
- Heat butter in a large pot or dutch oven. Add garlic, sliced onions and salt and cook over medium heat for 30 minutes. Remain at the stove, stirring every few minutes to ensure the onions do not burn.
- Add 1 teaspoon of sugar, turn the heat to low and cover with a lid. Continue cooking for approximately 50 minutes, until onions are golden brown and caramelized.
- Remove the lid and add flour to the caramelized onions. Mix well and cook for another 5 minutes.
- Add mushroom broth, Worcestershire sauce, sherry, thyme and cracked pepper and simmer for 20 minutes.
- Meanwhile, slice baguette in 1/2 inch rounds and toast until crunchy.
- Preheat oven to 350F.
- Line a baking sheet with aluminum foil. Place 4-6 oven proof bowls on the baking sheet and ladle soup into the bowls. Add 3 tbsp of shredded gruyere cheese to each bowl, mix well.
- Gently place one or two slices of bread on the top of each soup bowl then sprinkle with 1/4 cup of gruyere cheese per bowl.
- Place baking sheet in the oven and bake for 10 minutes, until cheese is melted and bubbling.
- Broil for 1-2 minutes, keeping an eye so the bread doesn’t burn. Serve immediately.
Nutrition
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