This French onion soup is deeply savory, rich with caramelized onions, and topped with bubbling, golden Gruyère. With a double-onion method for extra depth and silky texture, it tastes as if it came straight from a cozy Paris bistro.
French onion soup — soupe à l’oignon — has a bit of a reputation, but it’s far more doable than it seems. With butter, plenty of yellow onions, good beef broth, a splash of red wine and dry sherry, Worcestershire sauce for depth, and fresh thyme for warmth, you can build a deeply savory, restaurant-worthy soup right at home.
What truly sets this version apart is that I caramelize the onions in two batches. The first cooks down until it almost melts into the broth, adding body and rich, concentrated flavor. The second batch is caramelized just until silky and golden, giving you those beautiful strands in every spoonful. Finished with olive oil–tossed bread and bubbling Gruyère on top, it’s classic comfort with just a little extra magic.
Bon Appetit: Pro tips for an authentic French onion soup
I grew up loving the French onion soup that a family friend (and accomplished chef) taught me how to make. Here are the tips I learned to make the absolute best French onion soup:
- Low and slow: Caramelize the onions over steady medium heat until golden and jammy — rushing leads to burning, not depth.
- Double the onions: Cook one batch longer so it melts into the broth and adds body, while the second batch keeps those silky strands.
- Use great broth: Homemade beef stock is wonderful, but a quality store-bought (look for bone broth) works beautifully.
- Toast the bread: A lightly toasted baguette holds up under the broth and cheese without turning soggy.
Make it in a slow cooker
This French onion soup recipe can easily be adapted for the slow cooker. There are two ways you can approach this: either use a skillet to caramelize the onions or keep everything in the slow cooker.
- From skillet to slow cooker: To speed things up a bit, start by caramelizing your onions in a large pan. Once they’re done, transfer the caramelized onions to the slow cooker. I would call it a shortcut, but it’ll still take some time!
- Just the slow cooker: If you want to make your French onion soup entirely in the slow cooker, you can! Add the butter, onions, salt, and pepper directly into the slow cooker. Set your slow cooker to low, cover it, and let it cook for 10-12 hours, stirring every few hours if possible.
Once those onions are perfect, finish the recipe by adding flour, wine, sherry, broth, and thyme. Let it cook on low for another 2-3 hours to let those flavors really come together. When you’re ready to serve, ladle the soup into bowls, top with your toasted baguette and Gruyere, and broil until that cheese is all melty and golden.
French Onion Soup Recipe
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Ingredients
- ▢ 4 tablespoons butter (salted)
- ▢ 4 lb yellow onions (peeled and thinly sliced)
- ▢ 1 teasoon EACH: sea salt and pepper
- ▢ 2 tablesoons all-purpose flour
- ▢ 1 cup dry red wine
- ▢ 2 tablesoons dry sherry
- ▢ 6 cups beef bone broth (see notes)
- ▢ 1 tablespoon fresh thyme leaves
- ▢ 1 tablespoon Worcestershire sauce (optional – see notes)
The Topping
- ▢ 1 baguette (cut into cubes)
- ▢ 2 tablespoons olive oil
- ▢ 1 teaspoon Italian seasoning
- ▢ ¼ teaspoon EACH: salt and pepper
- ▢ 1 ½ cups grated gruyere
Instructions
- Melt the butter in a large soup pot over medium heat. Add HALF the sliced onions, the salt and pepper and stir well. Cover the pot and cook the onions for 30 minutes, stirring every 10 minutes. The onions will be wet and simmering in their own liquid. If they look like they’re boiling hard, reduce the heat to medium-low. 4 tablespoons butter, 4 lb yellow onions, 1 teasoon EACH: sea salt and pepper
- Add the remaining onions to the pot, cover, and cook for 10 minutes. Remove the lid, stir, and continue to cook with the lid off stirring every 5 minutes until the liquid has evaporated and the onions are golden, about 20 minutes more.
- Add the flour to the pot and stir well. Add the wine and sherry and simmer for a few minutes. Add the bone broth, thyme, and if using, Worcestershire sauce, and bring the pot to a simmer. Continue to let it simmer, uncovered, for 10 minutes. 2 tablesoons all-purpose flour, 1 cup dry red wine, 2 tablesoons dry sherry, 6 cups beef bone broth, 1 tablespoon fresh thyme leaves, 1 tablespoon Worcestershire sauce
- While the soup is cooking, make the croutons. Preheat your oven to 425 degrees Fahrenheit. Toss the bread cubes, olive oil, Italian seasoning, salt, and pepper in a large bowl until the bread is well-coated. Spread the croutons in a single layer on a baking sheet and toast in the oven for 12-15 minutes. You want them to be toasted but not hard. 1 baguette, 2 tablespoons olive oil, 1 teaspoon Italian seasoning, ¼ teaspoon EACH: salt and pepper
- When the soup has finished cooking, ladle it into ovenproof crocks and top with a handful of croutons and some gruyere. Place the crocks on a baking sheet (for easier handling) and broil them for 2-3 minutes, until the cheese has melted. Serve right away. 1 ½ cups grated gruyere
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Notes
Nutrition
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How to store leftovers?
It’s best to store the French onion soup base without the croutons and cheese on top. Once it’s cooled, transfer it to a covered container and refrigerate for up to 4 days. When reheating, bring it to a simmer on the stove and toast fresh croutons to serve with it.
Can I freeze French onion soup?
You can! Pop it in a freezer-proof container and store it for up to 3 months; however, freeze the soup without the croutons and cheese. Thaw it in the fridge a day before you wish to enjoy it. Reheat the soup on the stove, then add the croutons and cheese fresh, and broil it.
What type of cheese works best for French onion soup?
Gruyère is the classic choice for its nutty flavor and excellent melting properties. However, Swiss cheese, Emmental, or even mozzarella can work in a pinch if Gruyère cheese is unavailable.
Can I make French onion soup with garlic?
You might have noticed garlic cloves were not on the ingredients list. While this might sound like sacrilege to the garlic lovers among us, it’s not a traditional ingredient in a classic French onion soup. If you want, add a clove or two toward the end of the caramelizing process.
More of my favorite cozy soups
Broccoli Cheese Soup
Roasted Garlic Soup – Rich and Creamy
Tuscan Chicken Soup with Prosciutto and Parmesan
Italian Sausage Soup (My Mom’s Recipe!)
French Onion Soup Recipe
Ingredients
- 4 tablespoons butter , salted
- 4 lb yellow onions , peeled and thinly sliced
- 1 teasoon EACH: sea salt and pepper
- 2 tablesoons all-purpose flour
- 1 cup dry red wine
- 2 tablesoons dry sherry
- 6 cups beef bone broth , see notes
- 1 tablespoon fresh thyme leaves
- 1 tablespoon Worcestershire sauce , optional - see notes
The Topping
- 1 baguette , cut into cubes
- 2 tablespoons olive oil
- 1 teaspoon Italian seasoning
- ¼ teaspoon EACH: salt and pepper
- 1 ½ cups grated gruyere
Instructions
- Melt the butter in a large soup pot over medium heat. Add HALF the sliced onions, the salt and pepper and stir well. Cover the pot and cook the onions for 30 minutes, stirring every 10 minutes. The onions will be wet and simmering in their own liquid. If they look like they’re boiling hard, reduce the heat to medium-low. 4 tablespoons butter, 4 lb yellow onions, 1 teasoon EACH: sea salt and pepper
- Add the remaining onions to the pot, cover, and cook for 10 minutes. Remove the lid, stir, and continue to cook with the lid off stirring every 5 minutes until the liquid has evaporated and the onions are golden, about 20 minutes more.
- Add the flour to the pot and stir well. Add the wine and sherry and simmer for a few minutes. Add the bone broth, thyme, and if using, Worcestershire sauce, and bring the pot to a simmer. Continue to let it simmer, uncovered, for 10 minutes. 2 tablesoons all-purpose flour, 1 cup dry red wine, 2 tablesoons dry sherry, 6 cups beef bone broth, 1 tablespoon fresh thyme leaves, 1 tablespoon Worcestershire sauce
- While the soup is cooking, make the croutons. Preheat your oven to 425 degrees Fahrenheit. Toss the bread cubes, olive oil, Italian seasoning, salt, and pepper in a large bowl until the bread is well-coated. Spread the croutons in a single layer on a baking sheet and toast in the oven for 12-15 minutes. You want them to be toasted but not hard. 1 baguette, 2 tablespoons olive oil, 1 teaspoon Italian seasoning, ¼ teaspoon EACH: salt and pepper
- When the soup has finished cooking, ladle it into ovenproof crocks and top with a handful of croutons and some gruyere. Place the crocks on a baking sheet (for easier handling) and broil them for 2-3 minutes, until the cheese has melted. Serve right away. 1 ½ cups grated gruyere
