French Onion Soup Recipe: Deeply Caramelized, Cheesy Top

A steaming bowl of French onion soup is pure bistro comfort: sweet, jammy onions in a deeply savory broth, topped with a crisp slice of baguette and a thick layer of melted, bubbling Gruyère. It is the soup I crave the moment the weather turns cold, and making it at home is far easier than most people expect.

The secret is patience with the onions. Cooked slowly until they turn a rich mahogany color, they become incredibly sweet and give the soup its signature depth. In this guide I will show you exactly how to caramelize onions without burning them, how to build a broth with restaurant-level flavor, and how to get that perfect, golden cheese crust. The full printable recipe card is at the bottom of the post.

Why This French Onion Soup Works

French onion soup has only a handful of ingredients, so each step has a job. This recipe focuses on flavor-building techniques that turn humble onions into something extraordinary. Once you have made it a couple of times, you will find the rhythm is relaxing: slice, stir, wait and enjoy the aroma filling your kitchen.

• A mix of yellow and sweet onions. Yellow onions bring savory depth while sweet onions caramelize quickly and add natural sweetness.
• Low and slow caramelizing. About 45 minutes over medium-low heat develops rich, complex flavor without bitterness.
• Deglazing with wine. Dry white wine or sherry lifts the browned bits from the pot and adds brightness.
• Beef and chicken broth together. Beef broth gives richness while chicken broth keeps the soup from tasting too heavy.
• Gruyère plus a little Parmesan. Gruyère melts beautifully and is nutty; Parmesan adds a salty, savory edge.

The result is a French onion soup with layers of sweet, savory and nutty flavors, just like the one you would order in a Paris café. It is hearty enough to serve as a main course with a green salad, and elegant enough to start a dinner party. Making a big pot also means you can freeze portions of the base for quick, cozy lunches later in the season.

Ingredients You Need

This classic soup uses simple pantry and fridge staples. Exact amounts are in the recipe card below; here is what each ingredient contributes.

• Onions: about 3 pounds, thinly sliced from root to tip so they hold their shape.
• Butter and olive oil: butter for flavor, oil to keep it from burning during the long cook.
• Sugar and salt: a pinch of each helps the onions release moisture and brown evenly.
• Garlic and fresh thyme: aromatic support for the onions.
• Flour: a tablespoon lightly thickens the soup so it coats a spoon.
• Dry white wine or sherry: for deglazing and a lively backbone of flavor.
• Beef broth and chicken broth: use good-quality low-sodium broth so you can control the salt.
• Bay leaf and Worcestershire sauce: small additions that add surprising depth.
• Baguette: sliced and toasted until crisp so it does not go soggy.
• Gruyère and Parmesan: freshly grated for the best melt.

How to Make French Onion Soup

Most of the time is hands-off while the onions caramelize, so put on some music and give them a stir every few minutes. You can slice the onions up to a day ahead and keep them in a sealed container in the fridge, which makes this soup very manageable on a weeknight.

1. Caramelize the onions. Melt the butter with the olive oil in a large Dutch oven over medium heat. Add the onions, salt and sugar and stir to coat. Cook for 10 minutes until softened, then lower the heat to medium-low and cook for 35 to 45 minutes more, stirring every 5 minutes, until deep golden brown and jammy.
2. Add aromatics. Stir in the garlic and thyme and cook for 1 minute. Sprinkle in the flour and stir for 1 minute more.
3. Deglaze. Pour in the wine and scrape up all the browned bits from the bottom of the pot. Simmer for 2 minutes until the wine has mostly evaporated.
4. Simmer the soup. Add both broths, the bay leaf and Worcestershire sauce. Bring to a boil, then reduce the heat and simmer uncovered for 25 to 30 minutes. Taste and season with salt and pepper, and remove the bay leaf.
5. Toast the bread. Meanwhile, arrange baguette slices on a baking sheet, brush lightly with olive oil and bake at 400°F (200°C) for 8 to 10 minutes until crisp.
6. Broil with cheese. Ladle the soup into oven-safe crocks set on a baking sheet. Top each with toasted baguette, a thick handful of Gruyère and a sprinkle of Parmesan. Broil for 2 to 4 minutes until the cheese is bubbling and browned in spots.

Let the crocks cool for a couple of minutes before serving, as they will be very hot. Place each one on a small plate and serve with a crisp green salad dressed with a sharp vinaigrette to balance the richness. If you do not have oven-safe bowls, broil the cheese-topped toasts on a sheet pan and float them on the soup just before serving. A glass of the same dry white wine you cooked with is the perfect match.

Expert Tips for the Best Results

• Slice the onions evenly. Uniform slices caramelize at the same rate, so none burn while others stay pale.
• Use a heavy pot. A cast iron or enameled Dutch oven spreads heat evenly and prevents scorching.
• Do not rush the caramelizing. Turning up the heat browns the onions quickly but makes them bitter rather than sweet.
• Toast the bread well. Dry, crisp croutons hold up under the cheese and broth without dissolving.
• Watch the broiler closely. Cheese goes from golden to burnt in seconds, so keep the oven door slightly open and stay nearby.

Easy Variations to Try

This classic French onion soup is easy to adapt:

• Vegetarian: use rich mushroom or vegetable broth and a splash of soy sauce for savory depth.
• Slow cooker: caramelize the onions on the stove, then simmer the soup on low for 6 hours.
• Different cheeses: try Swiss, Comté, provolone or a mix of mozzarella and Parmesan.
• Gluten free: skip the flour and use gluten-free bread for the topping.
• French onion sliders: use the leftover caramelized onions and cheese on mini burgers.

Looking for more warming bowls? Browse our cozy soup and stew collection, serve it with our tender slow-cooked beef roast for a hearty feast, or end the meal with a molten chocolate dessert for two.

Common Mistakes and How to Fix Them

How to Store, Freeze and Reheat Onion Soup

Refrigerator: store the soup (without bread and cheese) in an airtight container for up to 4 days. The flavor improves overnight. Freezer: freeze the soup base for up to 3 months, leaving room at the top of the container for expansion.

Reheating: thaw overnight in the fridge, then bring to a simmer on the stove until steaming hot. Reheat leftovers to 165°F (74°C), following the USDA advice on leftovers. Add fresh toast and cheese and broil just before serving.

Frequently Asked Questions

Ready to cook? Here is the complete printable French onion soup recipe with exact amounts, times and estimated nutrition.

French Onion Soup

Slowly caramelized onions simmered in a rich beef broth, topped with toasted baguette and bubbling Gruyère.

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 1 hour hr 30 minutes mins

Total Time 1 hour hr 45 minutes mins

Servings: 6 bowls

Course: dinner, Soup, Starter

Cuisine: French

Calories: 430

Ingredients Method Notes

Ingredients

  

Soup

• 4 tablespoons unsalted butter
• 1 tablespoon olive oil
• 3 pounds yellow and sweet onions thinly sliced, about 5 large, 1.4 kg
• 1 teaspoon salt
• 1/2 teaspoon sugar
• 3 cloves garlic minced
• 1 teaspoon fresh thyme leaves
• 1 tablespoon all-purpose flour
• 1/2 cup dry white wine or dry sherry 120 ml
• 4 cups low-sodium beef broth 1 liter
• 2 cups low-sodium chicken broth 480 ml
• 1 bay leaf
• 1 teaspoon Worcestershire sauce

Topping

• 12 slices baguette 1/2 inch thick
• 2 cups Gruyère cheese grated, 200 g
• 1/4 cup Parmesan cheese grated

Method

 

1. Melt butter with oil in a Dutch oven over medium heat. Add onions, salt and sugar; cook 10 minutes, then reduce to medium-low and cook 35 to 45 minutes, stirring often, until deep golden.
2. Stir in garlic and thyme for 1 minute, then the flour for 1 minute.
3. Deglaze with wine, scraping up browned bits, and simmer 2 minutes.
4. Add both broths, bay leaf and Worcestershire. Simmer uncovered 25 to 30 minutes. Season and remove the bay leaf.
5. Toast baguette slices at 400°F (200°C) for 8 to 10 minutes until crisp.
6. Ladle soup into oven-safe crocks, top with bread, Gruyère and Parmesan, and broil 2 to 4 minutes until bubbling and browned.

Notes

Make ahead: the soup base keeps 4 days in the fridge or 3 months in the freezer.

Vegetarian: use mushroom broth and a splash of soy sauce.

Nutrition is an estimate per bowl with topping.

I hope this French onion soup warms up your cold evenings as much as it does mine. If you make it, leave a comment and a star rating below. I would love to hear which cheese you chose!