Slow-Cooked French Onion Soup
Slow-cooked onions, rich savory broth, toasted bread, and bubbling melted cheese come together in this classic French Onion Soup. The secret is slowly caramelizing the onions until they’re deeply golden and sweet, creating a rich flavor that makes this comforting soup perfect for a cozy family dinner.
Ingredients
- 4 large yellow onions, thinly sliced
- 3 tablespoons butter
- 1 tablespoon olive oil
- 2 cloves garlic, minced
- 1 teaspoon sugar, optional
- 6 cups beef broth
- 1 cup chicken broth
- ½ cup dry white wine, optional
- 1 teaspoon Worcestershire sauce
- 1 teaspoon dried thyme
- 1 bay leaf
- ½ teaspoon salt
- ½ teaspoon black pepper
- 1 baguette, sliced
- 1½–2 cups shredded Gruyère or Swiss cheese
- ¼ cup grated Parmesan cheese, optional
Directions
1. Slowly Cook the Onions
Melt the butter with the olive oil in a large heavy-bottomed pot over medium-low heat.
Add the sliced onions and a pinch of salt. Stir to coat them with the butter.
Cook slowly for 35–50 minutes, stirring every few minutes, until the onions become deeply golden brown and caramelized.
If they begin sticking or browning too quickly, reduce the heat and add a tablespoon of water.
2. Add the Garlic
Stir in the minced garlic and cook for about 1 minute.
Add the sugar if desired. It can help encourage browning, although properly cooked onions will naturally become sweet.
3. Deglaze the Pot
Pour in the white wine if using.
Scrape the bottom of the pot with a wooden spoon to loosen all the browned bits.
Allow the wine to simmer for 2–3 minutes.
4. Add the Broth
Pour in the beef broth and chicken broth.
Add the Worcestershire sauce, thyme, bay leaf, black pepper, and remaining salt.
Bring the soup to a gentle simmer.
Reduce the heat, cover partially, and cook for 25–30 minutes.
Remove the bay leaf before serving.
5. Toast the Bread
While the soup simmers, preheat your oven to 400°F (200°C).
Arrange baguette slices on a baking sheet and toast for approximately 5–8 minutes, until crisp and lightly golden.
6. Add the Cheese
Ladle the hot soup into oven-safe bowls.
Place one or two toasted baguette slices on top of each bowl.
Generously cover the bread with shredded Gruyère or Swiss cheese.
Add a little Parmesan if desired.
7. Broil Until Golden
Place the bowls carefully on a baking sheet.
Broil for 2–4 minutes, watching closely, until the cheese melts, bubbles, and becomes beautifully golden brown.
Allow the bowls to cool for a few minutes before serving—the soup and bowls will be extremely hot.
Tips for Perfect French Onion Soup
Don’t rush the onions: Deep caramelization is what gives this soup its signature flavor.
Use good broth: Since broth makes up most of the soup, a flavorful beef broth makes a noticeable difference.
Choose sturdy bread: A baguette holds up better than soft sandwich bread.
Use plenty of cheese: Gruyère melts beautifully and develops a delicious golden crust.
Watch the broiler: Cheese can go from perfectly browned to burned very quickly.
Easy Variations
For a richer soup, add a splash of heavy cream at the end, although traditional French onion soup is usually broth-based.
For a vegetarian version, replace the beef broth with a rich vegetable broth or mushroom broth.
You can also use Swiss, provolone, or mozzarella if Gruyère isn’t available.
Storage
Store the soup without the bread and cheese topping in an airtight container in the refrigerator for up to 4 days.
Reheat gently on the stovetop, then add fresh toasted bread and cheese before broiling.
Recipe at a Glance
Prep Time: 15 minutes
Cook Time: 1–1½ hours
Total Time: About 1½ hours
Servings: 6
Difficulty: Easy to Moderate
Meta Description
Make comforting French Onion Soup with slowly caramelized onions, rich savory broth, toasted baguette, and bubbling melted cheese. A classic cozy meal perfect for chilly days.