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This classic French onion soup is the ultimate comfort food, celebrated for its rich, deeply caramelized onions simmered in a savory, aromatic broth and topped with perfectly toasted, cheesy croutons.
The slow caramelization process develops a complex sweetness and umami depth that makes every spoonful incredibly satisfying.
Nutritionally, it’s a balanced dish offering a hearty 31 grams of protein per serving, mainly from the Gruyère and Parmigiano cheeses and beef broth, which help keep you full and energized.
While indulgent with a moderate fat content, the recipe features good fats from butter and cheese, and offers a modest 4 grams of fiber thanks to the onions and bread.
It’s also relatively low in carbs for a soup with bread, making it a great option for those watching their carbohydrate intake but craving warmth and flavor.
This soup is perfect for everyday cooking because it’s straightforward, meal-prep friendly (make-ahead and freezes well), and delivers comforting, satisfying results with simple pantry staples.
Must-Have Tools for Perfect Results
Dutch Oven
Essential for even heat distribution and slow caramelization of onions, a Dutch oven ensures the soup’s rich flavors develop perfectly.
Beyond this recipe, it’s a versatile workhorse ideal for soups, stews, and braises.
Wooden Spoon
Perfect for stirring the onions gently without damaging the pot’s surface.
Wooden spoons are gentle on cookware and help prevent scorching, making them indispensable in any kitchen.
Ovenproof Soup Crocks
These allow for broiling the cheesy topping directly on the soup for that signature golden crust.
They’re also great for individual servings of casseroles, baked dips, and more.
Baking Sheet
Used for crisping baguette slices evenly before topping.
A sturdy baking sheet is a kitchen staple for roasting, baking, and broiling a variety of dishes.
Cheese Grater
A good-quality grater is key for shredding Gruyère and Parmigiano Reggiano finely and evenly, enhancing melting and flavor release.
It’s also useful for many other cooking and baking tasks.
Classic French Onion Soup
Equipment
- 1 large Dutch oven or heavy soup pot
- 1 Wooden Spoon
- Ovenproof soup crocks (4 to 6)
- 1 Baking Sheet
- Cheese grater
Ingredients
- 4 tablespoons unsalted butter
- 1 tablespoon vegetable oil
- 3 pounds sweet onions such as Vidalia, halved and thinly sliced
- ¾ teaspoon salt
- ½ teaspoon freshly ground black pepper
- ¾ teaspoon granulated sugar
- 1 cup dry white wine
- 2 tablespoons all-purpose flour
- 6 cups beef broth
- 1 teaspoon Worcestershire sauce
- ½ teaspoon dried thyme
- 2 bay leaves
- 1 small baguette sliced into ½-inch rounds
- 1 tablespoon dry sherry
- 8 ounces Gruyère cheese shredded (about 2 cups)
- ½ cup grated Parmigiano Reggiano cheese
Instructions
- Caramelize the Onions: In a large heavy-bottomed pot or Dutch oven, melt the butter over medium heat. Add the vegetable oil, then toss in the sliced onions along with salt, pepper, and sugar. Cook the onions uncovered, stirring occasionally at first. As the onions begin to soften and turn golden, stir more frequently to prevent sticking or burning. The goal is a deep golden brown and richly caramelized onion base, which usually takes about 45 to 55 minutes. If the onions start to stick or brown too fast, lower the heat or splash a little water to deglaze the pan.
- Deglaze and Reduce with Wine: Raise the heat to medium-high and pour in the white wine. Use a wooden spoon to scrape up any browned bits from the bottom of the pot. Let the wine simmer and reduce until nearly evaporated and the onions become jammy, about 8 to 10 minutes.
- Thicken the Base: Sprinkle the flour evenly over the onions and stir continuously for about one minute to cook the raw flour taste out. This helps thicken the broth later.
- Add Broth and Herbs: Pour in the beef broth, then add Worcestershire sauce, dried thyme, and bay leaves. Stir everything to combine, bring the soup to a boil, then reduce to a gentle simmer. Cover the pot and let it cook for 30 minutes, allowing the flavors to meld beautifully.
- Prepare the Toasted Bread: While the soup simmers, preheat your oven to 400°F (200°C). Arrange the baguette slices in a single layer on a baking sheet. Bake for about 10 minutes or until they are dry, crisp, and slightly golden around the edges. Set aside.
- Finish the Soup Flavor: Once the simmering is complete, remove and discard the bay leaves. Stir in the dry sherry, then taste and adjust seasoning as needed. Add a splash more Worcestershire sauce for depth or a pinch of sugar if the soup needs a touch more sweetness.
- Assemble and Broil: Position an oven rack about 6 inches from the broiler and preheat the broiler. Ladle the hot soup into oven-safe crocks or bowls. Top each serving with one or two toasted baguette slices, making sure not to overlap. Sprinkle a generous layer of Gruyère and Parmigiano Reggiano cheeses on top. Place the crocks on a baking sheet and broil until the cheese melts, bubbles, and develops golden edges, approximately 3 to 5 minutes.
- Serve Carefully: Remove the crocks from the oven and allow them to cool slightly before serving to avoid burns. Enjoy your rich, comforting French onion soup!
Notes
Chef’s Expert Tips For Success
Mastering French onion soup hinges on patience, especially when caramelizing the onions.
Cooking them low and slow allows their natural sugars to develop into a deep, rich sweetness, which forms the backbone of the soup’s flavor.
Avoid rushing this step by keeping the heat moderate and stirring often to prevent burning.
Deglazing the pan with dry white wine helps lift the flavorful browned bits, adding complexity.
Using a good-quality beef broth and authentic cheeses like Gruyère and Parmigiano Reggiano elevates the taste dramatically.
When broiling, watch the cheese closely to achieve that perfect bubbly, golden crust without burning.
For an even richer profile, adding a splash of dry sherry at the end brightens the flavor beautifully.
Lastly, if you don’t have ovenproof crocks, feel free to broil the cheese separately on toasted bread and add to the soup—this flexibility means great soup no matter your kitchen setup.
Delicious Serving Suggestions To Try
French onion soup is a versatile starter or a hearty meal on its own.
Serve it alongside a crisp green salad with a tangy vinaigrette to balance the richness of the soup.
A simple side of roasted vegetables or steamed green beans pairs nicely without overwhelming the palate.
For wine lovers, a dry white like Sauvignon Blanc or a light red such as Pinot Noir complements the soup’s caramelized onion flavors perfectly.
You can also try topping the soup with a sprinkle of fresh thyme or a drizzle of truffle oil just before serving to add an aromatic twist.
For a casual gathering, offer crusty bread with olive oil and herbs to soak up the broth alongside the cheesy croutons.
Best Storage Tips For Longevity
Store any leftover French onion soup without the toasted bread and cheese in an airtight container in the refrigerator.
It will keep well for up to three days, making it a convenient make-ahead meal.
When reheating, warm the soup gently on the stovetop to avoid overcooking or breaking down the onions further.
Prepare the toasted baguette slices separately, and add the cheese just before broiling to maintain their crispness.
If you want to freeze the soup, do so without bread and cheese, in freezer-safe containers, for up to three months.
Thaw overnight in the fridge and reheat slowly for the best texture and flavor preservation.
Frequently Asked Questions Answered
1. Can I make this soup vegetarian?
Absolutely! Substitute the beef broth with a rich vegetable broth and omit the Worcestershire sauce or use a vegetarian version. The caramelized onions and cheese will still provide robust flavor.
2. What onions work best?
Sweet onions like Vidalia or Walla Walla are ideal for caramelizing due to their natural sugars, but yellow onions are a great, more affordable alternative.
3. How do I prevent the soup from being too salty?
Use low-sodium beef broth and taste the soup before adding extra salt. Adjust seasoning gradually, especially since the cheese topping adds saltiness.
4. Can I prepare the soup ahead of time?
Yes! The soup base can be made up to three days in advance and refrigerated. Toast the bread and add cheese only when ready to serve for the freshest results.
5. What can I substitute for Gruyère cheese?
Emmental or Swiss cheese work well as alternatives due to their excellent melting qualities and similar nutty flavors.
This recipe is inspired by onceuponachef and has been carefully refined to enhance clarity, streamline preparation steps, and ensure accurate results. We’ve also included health benefits, nutritional highlights, and Must-Have Tools to help you get the best results every time you cook.