French Onion Soup

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French Onion Soup is a timeless French classic featuring deeply caramelized onions simmered in a rich beef broth, topped with toasted baguette slices and melted Gruyère cheese. While it takes some time to caramelize the onions properly, the result is an incredibly flavorful, comforting soup that’s perfect for chilly evenings or elegant dinners.

Recipe Information

  • Prep Time: 15 minutes
  • Cook Time: 1 hour 20 minutes
  • Total Time: 1 hour 35 minutes
  • Servings: 6
  • Difficulty: Moderate

Ingredients

For the Soup

  • 4 large yellow onions (about 2½ pounds), thinly sliced
  • 3 tablespoons unsalted butter
  • 2 tablespoons olive oil
  • 2 cloves garlic, minced
  • 1 teaspoon sugar (optional, helps caramelization)
  • 1 teaspoon salt
  • ½ teaspoon black pepper
  • 2 tablespoons all-purpose flour
  • ½ cup dry white wine (optional)
  • 6 cups beef broth (low sodium preferred)
  • 1 cup chicken broth (adds depth, optional)
  • 1 tablespoon Worcestershire sauce
  • 2 sprigs fresh thyme (or 1 teaspoon dried thyme)
  • 1 bay leaf

For the Topping

  • 6 slices French baguette
  • 2 tablespoons olive oil or melted butter
  • 2 cups shredded Gruyère cheese
  • ½ cup grated Parmesan cheese (optional)

Equipment

  • Large Dutch oven or heavy-bottomed pot
  • Wooden spoon
  • Baking sheet
  • Oven-safe soup bowls (ramekins or crocks)
  • Broiler

Instructions

Step 1: Caramelize the Onions

Heat the butter and olive oil in a large pot over medium heat.

Add the sliced onions, salt, pepper, and sugar (if using).

Cook, stirring every few minutes, for 40–50 minutes, until the onions become soft, golden brown, and deeply caramelized. Lower the heat if they begin to burn.

Tip: Proper caramelization is the secret to authentic French onion soup. Be patient—don’t rush this step.

Step 2: Add Garlic

Stir in the minced garlic and cook for 1 minute until fragrant.

Step 3: Make the Base

Sprinkle the flour over the onions and stir well.

Cook for 2 minutes to remove the raw flour taste.

Pour in the white wine (if using) and scrape up any browned bits from the bottom of the pot. Let it simmer for 2–3 minutes.

Step 4: Simmer the Soup

Add:

  • Beef broth
  • Chicken broth
  • Worcestershire sauce
  • Thyme
  • Bay leaf

Bring the soup to a gentle boil.

Reduce the heat and simmer for 25–30 minutes.

Remove the thyme sprigs and bay leaf before serving.

Taste and adjust with more salt and pepper if needed.

Step 5: Toast the Bread

Preheat the oven to 400°F (200°C).

Brush the baguette slices with olive oil or melted butter.

Toast for 8–10 minutes, turning once, until crisp and golden.

Step 6: Assemble

Ladle the hot soup into oven-safe bowls.

Place one or two toasted baguette slices on top of each bowl.

Cover generously with Gruyère cheese and sprinkle with Parmesan, if using.

Step 7: Broil

Place the bowls on a baking sheet.

Broil for 2–4 minutes, or until the cheese is melted, bubbly, and lightly browned.

Watch carefully to prevent burning.

Serving Suggestions

Serve hot with:

  • Caesar salad
  • Roasted vegetables
  • Grilled steak
  • Roast chicken
  • Crusty artisan bread
  • A glass of dry white wine

Storage

Refrigerator

Store cooled soup (without bread and cheese) in an airtight container for up to 4 days.

Freezer

Freeze the soup base for up to 3 months. Thaw overnight in the refrigerator, reheat gently, then add fresh toasted bread and cheese before broiling.

Tips for Success

  • Use yellow onions for the best balance of sweetness and flavor.
  • Caramelize the onions slowly over medium to low heat for maximum depth.
  • A good-quality beef broth makes a noticeable difference.
  • Toast the bread well so it holds up in the soup.
  • Gruyère melts beautifully and gives the soup its signature nutty flavor, but Swiss cheese can be used if needed.
  • Always broil in oven-safe bowls and monitor closely.

Variations

Vegetarian French Onion Soup

Replace the beef and chicken broth with a rich vegetable broth and use vegetarian Worcestershire sauce.

Richer Version

Add a splash of brandy or sherry after caramelizing the onions and let it cook off before adding the broth.

Creamy Version

Stir in ¼ cup heavy cream just before serving for a silkier texture.

Mushroom French Onion Soup

Add 8 ounces of sliced mushrooms during the last 10 minutes of caramelizing the onions.

Approximate Nutrition (Per Serving)

  • Calories: 430
  • Protein: 18 g
  • Carbohydrates: 29 g
  • Fat: 27 g
  • Saturated Fat: 13 g
  • Fiber: 3 g
  • Sugar: 8 g
  • Sodium: 980 mg

Why You’ll Love This Recipe

This classic French Onion Soup is rich, savory, and deeply satisfying. The slow-caramelized onions create a naturally sweet, complex flavor that pairs perfectly with the robust broth, crisp toasted baguette, and bubbling Gruyère cheese. Whether served as a cozy appetizer or a hearty main course, it’s a restaurant-quality dish that’s sure to impress family and guests alike.

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