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Appetizing close-up of classic french onion soup in a white crock, topped with bubbly melted cheese and a golden baguette slice.

Classic French Onion Soup

A soul-warming bowl of deeply caramelized onions in rich broth, topped with a golden, cheesy baguette slice — this classic French onion soup is a comforting gourmet staple.
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Prep Time 20 minutes
Cook Time 1 hour 5 minutes
Total Time 1 hour 25 minutes
Servings: 5 bowls
Course: Main Course, Soup
Cuisine: French
Calories: 480
Ingredients Equipment Method Notes

Ingredients
  

  • 4 tbsp unsalted butter
  • 5 large yellow onions, thinly sliced
  • 1 tsp salt
  • 1 tsp granulated sugar
  • 2 cloves garlic, minced
  • 32 oz low-sodium beef broth
  • 24 oz low-sodium chicken broth
  • 1 tbsp Worcestershire sauce
  • 2 sprigs fresh thyme
  • 1 bay leaf
  • 0.5 tbsp balsamic vinegar
  • 1 pinch freshly ground black pepper (to taste)
  • 5 1-inch thick French bread slices
  • 2 tbsp olive oil
  • 1.5 cups shredded Gruyère Swiss cheese, room temperature
  • 0.25 cup shredded Mozzarella cheese, room temperature
  • 2 tbsp finely grated Parmesan cheese, room temperature

Equipment

  • Large Dutch oven or heavy-bottomed pot
  • Oven-safe soup crocks
  • Baking sheet
  • Sharp knife

Method
 

  1. In a large Dutch oven, melt butter over medium-high heat. Add sliced onions and sauté for 10 minutes until softened. Reduce heat to medium, add salt and sugar, and continue cooking for 35 minutes, stirring every 5 minutes until deeply caramelized.
  2. Add minced garlic and cook until fragrant, about 20 seconds. Stir in beef broth, chicken broth, Worcestershire sauce, thyme, and bay leaf. Simmer for 20 minutes, then remove thyme and bay leaf. Add balsamic vinegar and season to taste.
  3. Preheat broiler. Brush both sides of French bread slices with olive oil and place on a baking sheet. Broil for 2-3 minutes, flipping once, until golden and toasted.
  4. Place soup crocks on a baking sheet. Ladle hot soup into each bowl. Top each with a toast slice and sprinkle Gruyère, Mozzarella, and Parmesan on top. Broil until cheese is melted and golden, about 2–4 minutes.

Notes

Use yellow onions for best flavor. A blend of Gruyère, Mozzarella, and Parmesan creates the perfect melty topping. Prepare soup base ahead of time and broil toasts fresh for serving. Deglaze the pot thoroughly to build flavor. Monitor broiler closely while toasting cheese.