Classic French Onion Soup With Gruyère Cheese

French onion soup is made from very simple things: onions, butter, broth, bread and cheese. What makes it special is time. The onions cook slowly for about 45–60 minutes until they turn soft, sweet and deep golden brown. That slow cooking, called caramelizing, is where all the flavor comes from. This classic French onion soup with Gruyère cheese walks you through it step by step, then finishes with a crunchy toast and bubbly, browned Gruyère on top.

Quick Facts

• Prep time: 15 minutes
• Cook time: about 1 hour 30 minutes
• Total time: about 1 hour 45 minutes
• Servings: 4–6
• Difficulty: Medium (easy steps, but needs patience)
• Equipment: heavy pot or Dutch oven, oven-safe soup bowls, baking sheet

Ingredients

• 3 lb (1.4 kg) yellow onions (about 5 large), thinly sliced
• 4 tablespoons (55 g) unsalted butter
• 1 tablespoon olive oil
• 1 teaspoon salt (plus more to taste)
• 1 teaspoon sugar (optional, helps browning)
• 3 cloves garlic, minced
• ½ cup (120 ml) dry white wine or dry sherry (or more broth)
• 2 tablespoons all-purpose flour
• 6 cups (1.4 liters) beef broth (low-sodium is best)
• 2 sprigs fresh thyme (or ½ teaspoon dried)
• 1 bay leaf
• 1 teaspoon Worcestershire sauce
• ¼ teaspoon black pepper
• 1 small baguette, cut into ¾-inch slices
• 2 cups (about 200 g) Gruyère cheese, shredded

Why Gruyère? It melts smoothly, browns nicely and has a nutty, slightly sweet taste. Swiss cheese is a cheaper substitute.

Step 1: Caramelize the Onions (The Most Important Step)

1. Slice evenly. Cut onions in half from top to root, peel, and slice into thin half-moons, about ⅛ inch thick. Even slices cook at the same speed.

2. Start covered. Melt the butter with the oil in a large heavy pot over medium heat. Add the onions and salt. Stir to coat. Cover and cook for 15 minutes, stirring a few times. This softens the onions and lets them release their water.

3. Uncover and go low and slow. Remove the lid, add the sugar, and turn the heat to medium-low. Cook for 40–50 minutes, stirring every 5 minutes or so.

4. Watch the color change. The onions will go from white → pale yellow → golden → deep amber brown, like the color of caramel or maple syrup. They'll shrink to about one-quarter of their starting size.

5. Scrape the brown bits. Brown bits will form on the bottom of the pot. That's flavor! If they start getting too dark, add 1–2 tablespoons of water and scrape them up.

Don't rush this by turning up the heat. High heat burns the outside of the onions before they get sweet, and the soup tastes bitter.

Step 2: Build the Soup

1. Add garlic. Stir in the garlic and cook for 1 minute.
2. Deglaze. Pour in the wine or sherry. Scrape the bottom well and cook until most of the liquid is gone, about 2–3 minutes.
3. Add flour. Sprinkle in the flour and stir for 1 minute. This thickens the soup slightly.
4. Add broth and herbs. Slowly stir in the beef broth. Add the thyme, bay leaf, Worcestershire sauce and pepper.
5. Simmer. Bring to a gentle boil, then lower the heat and simmer uncovered for 25–30 minutes.
6. Taste. Remove the bay leaf and thyme stems. Add salt if needed.

Step 3: Toast and Broil

1. Toast the bread. Heat the oven to 400°F (200°C). Place baguette slices on a baking sheet and bake for 6–8 minutes until dry and lightly golden. Toasted bread holds up better in the soup.
2. Switch to broil. Move an oven rack about 6 inches below the broiler and turn the broiler on high.
3. Fill the bowls. Place oven-safe bowls on a baking sheet (this makes them easier and safer to move). Ladle soup into each bowl.
4. Top. Place 1–2 toasts on each bowl and cover generously with Gruyère, letting some hang over the edges.
5. Broil for 2–4 minutes, until the cheese is bubbly with brown spots. Watch closely, because cheese burns fast.
6. Careful! The bowls will be extremely hot. Use oven mitts and serve on a plate.

No oven-safe bowls? Put the toasts on the baking sheet, top with cheese, broil until bubbly, then float them on top of the soup in regular bowls.

Tips

• Yellow onions are best. They become sweet and rich. Red onions turn a dull color; sweet onions can get too sugary.
• Use a wide, heavy pot. More space means more browning and less steaming.
• Use good broth. It makes up most of the soup, so choose one you like the taste of.
• Make it ahead. The soup tastes even better the next day. Broil the cheese just before serving.

Common Problems

The soup tastes bland. The onions weren't browned enough, or it needs salt. Season and simmer a little longer.

The soup is bitter. The onions burned. Next time, use lower heat and add water when the bottom gets dark.

The bread got soggy. It wasn't toasted enough. Toast it until dry all the way through.

The cheese didn't brown. The rack was too far from the broiler. Move it closer and watch carefully.

Variations

• Vegetarian: Use a rich mushroom or vegetable broth and a little soy sauce instead of Worcestershire.
• Slow cooker onions: Cook the sliced onions with butter in a slow cooker on LOW for 10 hours, stirring once or twice, then continue on the stove.
• Alcohol-free: Use extra broth plus 1 teaspoon balsamic vinegar.
• Cheese mix: Use half Gruyère and half provolone or mozzarella for extra stretch.

What to Serve With It

French onion soup is filling, so a light side is best: a crisp green salad with vinaigrette, or roasted vegetables. For a soup-and-sandwich meal, a warm chicken pesto panini is a nice match.

Storage, Freezing and Reheating

Fridge: Store the soup (without bread and cheese) in airtight containers for 3–4 days.

Freezer: The soup freezes very well without the toppings. Freeze for up to 3 months. Thaw overnight in the fridge.

Reheat: Warm on the stove over medium heat until steaming, then add fresh toast and cheese and broil.

Nutrition Estimate

Per serving (1/6 of the recipe, with bread and cheese):

• Calories: about 420
• Protein: about 19 g
• Carbohydrates: about 38 g
• Fat: about 20 g
• Sodium: about 1,000 mg (less with low-sodium broth)

FAQs

How long does it take to caramelize onions?

About 45–60 minutes in total. There's no real shortcut that gives the same deep flavor.

Can I use chicken broth?

Yes, but the soup will be lighter in color and flavor. Mixing half beef and half chicken broth works well.

Does the alcohol cook off?

Most of it does during simmering, but not all. Use extra broth with a little vinegar if you want no alcohol.

What kind of bread is best?

A crusty baguette or country bread. Soft sandwich bread falls apart.

More Recipes to Try

• Easy Slow Cooker Beef Stew (coming soon)
• Crockpot Chicken Tortilla Soup (coming soon)
• Old Fashioned Buttermilk Biscuits From Scratch (coming soon)
• Chicken Pesto Panini Without a Panini Press
• Browse all recipes

A Final Note

Put on some music, keep the heat low, and give the onions the time they need. That patience is the real secret ingredient in a great bowl of French onion soup.