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French Onion Soup with Gruyere, Mozzarella, and Balsamic Vinegar Recipe

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★★★★★

4.5 from 128 reviews

This classic French Onion Soup recipe features caramelized yellow onions simmered in a rich broth with red wine and herbs, topped with toasted French bread slices and a blend of melted Gruyere, Mozzarella, and Parmesan cheeses for an indulgent and comforting dish.

Ingredients

Scale

Soup Base

  • 4 tablespoons unsalted butter
  • 5 large yellow onions, thinly sliced
  • 1 teaspoon salt
  • 1 teaspoon granulated sugar
  • 2 cloves garlic, minced
  • 1/2 cup dry red wine
  • 32 ounces low-sodium beef broth
  • 24 ounces low-sodium chicken broth
  • 1 tablespoon Worcestershire sauce
  • 2 sprigs fresh thyme
  • 1 bay leaf
  • 1/2 tablespoon balsamic vinegar
  • Pinch of salt and freshly ground black pepper, to taste

Toppings

  • 5 1-inch thick slices of French bread
  • 2 tablespoons olive oil
  • 1 1/2 cups shredded Gruyere Swiss cheese, room temperature
  • 1/4 cup shredded Mozzarella cheese, room temperature
  • 2 tablespoons finely grated Parmesan cheese, room temperature

Instructions

  1. Caramelize the Onions: In a large pot or Dutch oven, melt the unsalted butter over medium heat. Add the thinly sliced yellow onions, salt, and granulated sugar, stirring occasionally. Cook the onions slowly for about 45 minutes until deeply caramelized and golden brown, which develops their natural sweetness and rich flavor.
  2. Add Garlic and Wine: Stir in the minced garlic and cook for about 1 minute until fragrant. Then pour in the dry red wine to deglaze the pot, scraping up any browned bits stuck to the bottom. Let the wine reduce by half, concentrating its flavor.
  3. Add Broth and Seasonings: Add the low-sodium beef broth, chicken broth, Worcestershire sauce, fresh thyme sprigs, bay leaf, and balsamic vinegar. Bring the soup to a simmer, then reduce heat to low and simmer gently for 30 minutes to meld the flavors together. Adjust seasoning with salt and freshly ground black pepper to taste.
  4. Prepare the Bread: While the soup simmers, preheat your oven to 400°F (200°C). Brush both sides of the French bread slices lightly with olive oil. Place them on a baking sheet and toast in the oven for about 8-10 minutes until crisp and golden.
  5. Assemble and Broil: Remove the thyme sprigs and bay leaf from the soup. Ladle the hot soup into oven-safe bowls. Place one slice of toasted bread on top of each bowl and generously sprinkle the Gruyere, Mozzarella, and Parmesan cheeses over the bread. Place the bowls on a baking sheet and broil in the oven until the cheese is bubbling and golden brown, about 3-5 minutes. Watch carefully to avoid burning.
  6. Serve: Carefully remove the bowls from the oven and let cool slightly before serving. Enjoy your decadent, warm French Onion Soup with melted cheesy topping!

Notes

  • Dry red wine adds depth to the soup; if unavailable, substitute with additional beef broth or a splash of red grape juice.
  • Using low-sodium broths allows you to better control the saltiness of the soup.
  • Caramelizing onions properly is key to a rich soup flavor—take your time to avoid burning them.
  • Oven-safe bowls are recommended for broiling the cheese topping; if unavailable, individual ramekins or a large oven-safe dish can be used.
  • Leftover soup can be stored refrigerated for up to 3 days; reheat gently on the stovetop.

Keywords: French Onion Soup, caramelized onions soup, cheesy French soup, classic French recipe

Find it online: https://busyrecipe.com/french-onion-soup-with-gruyere-mozzarella-and-balsamic-vinegar-recipe/