French Onion Soup (Deep, Caramelized, Cheesy-Topped Classic)

French onion soup is proof that a handful of humble ingredients can turn into something restaurant-worthy. Onions cook low and slow until they are deep amber and sweet, beef broth and a splash of wine build the base, and the whole bowl goes under the broiler with toasted bread and a thick blanket of Gruyere. Crack through that golden cheese cap and the rich, savory soup underneath is pure comfort.

Serve it as a starter or pair it with a simple salad for a light supper. For more cozy bowls, try Easy Lasagna Soup and Slow Cooker Chicken Tortilla Soup.

Why This Recipe Works

• Patient caramelization: Cooking the onions low and slow for 35 to 40 minutes builds the deep sweetness that defines the soup.
• A splash of wine: Dry white wine or sherry lifts the browned bits from the pot and adds bistro depth.
• Oven-safe bowls: Broiling the assembled bowls melts the cheese into a bubbling, golden cap that seals in the heat.
• Sturdy bread: Thick toasted baguette slices hold up under the broth instead of turning to mush.

Ingredients

• 4 large yellow onions (about 900 g), halved and thinly sliced
• 3 tablespoons (45 g) unsalted butter
• 1 tablespoon (15 ml) olive oil
• 1 teaspoon (5 g) fine salt
• 1/2 teaspoon (1 g) black pepper
• 1 teaspoon (4 g) granulated sugar
• 2 cloves garlic, minced
• 1 tablespoon (15 g) all-purpose flour
• 1/2 cup (120 ml) dry white wine or dry sherry
• 6 cups (1.4 L) low-sodium beef broth
• 1 tablespoon (15 ml) Worcestershire sauce
• 2 sprigs fresh thyme
• 1 bay leaf
• 4 thick slices baguette, toasted
• 1 1/2 cups (150 g) shredded Gruyere cheese
• 1/2 cup (50 g) shredded Parmesan cheese
• Fresh chives or thyme leaves, to garnish

(full list in card)

Second photo: French Onion Soup Sainte-Foy-Tarentaise by WestportWiki, CC BY-SA 4.0, via Wikimedia Commons.

How to Make French Onion Soup

Step 1: Caramelize the onions

Melt the butter with the olive oil in a large heavy pot over medium heat. Add the onions, salt, pepper, and sugar. Cook, stirring often, for 35 to 40 minutes, until the onions are deep golden brown and sweet. If they brown too fast, lower the heat and add a splash of water.

Step 2: Build the broth

Stir in the garlic and cook for 1 minute. Sprinkle over the flour and stir for 1 minute more. Pour in the wine, scraping up the browned bits, and simmer for 2 minutes. Add the beef broth, Worcestershire sauce, thyme, and bay leaf.

Step 3: Simmer

Bring to a gentle simmer and cook, partly covered, for 20 minutes. Remove the thyme sprigs and bay leaf, and season to taste with salt and pepper.

Step 4: Assemble and broil

Heat the broiler. Ladle the soup into 4 oven-safe bowls and set them on a baking sheet. Top each with a toasted baguette slice and a generous handful of Gruyere and Parmesan. Broil for 3 to 5 minutes, watching closely, until the cheese is bubbly and golden in spots. Garnish with chives and serve at once.

Tips

• Do not rush the onions: Pale, quickly cooked onions give a thin, sharp soup. Deep amber color is where the flavor lives.
• Use a heavy pot: A Dutch oven or heavy-bottomed pot browns the onions evenly without scorching.
• Check your bowls: Only use bowls labeled broiler-safe, and always set them on a baking sheet for easy handling.
• Make the soup ahead: The broth keeps well for 2 days in the fridge; assemble and broil just before serving.

Storage

Refrigerate the soup base (without bread and cheese) in an airtight container for up to 4 days. Reheat gently on the stove, then assemble and broil as directed. Freeze the base for up to 3 months; thaw overnight in the fridge before reheating. Assembled bowls do not store well, since the bread softens.

Frequently Asked Questions

What onions are best for French onion soup?

Yellow onions are the classic choice: they turn sweet and deeply golden when caramelized. Sweet onions also work, while red onions give a darker, slightly sharper soup.

Can I make French onion soup without wine?

Yes. Skip the wine and add an extra 1/2 cup (120 ml) of beef broth plus 1 teaspoon of balsamic vinegar for a little brightness.

What cheese goes on French onion soup?

Gruyere is the traditional pick because it melts smoothly and tastes nutty and rich. A little Parmesan adds saltiness and helps the top brown.

Why is my soup bland?

It usually needs more caramelization time, more salt, or a longer simmer. Taste after simmering and adjust the salt, and make sure the onions reached a deep amber color before adding the broth.