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The Best Classic French Onion Soup with Deeply Caramelized Onions

Close-up of a rich bowl of french onion soup topped with a thick, browned layer of melted cheese over toast.
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Achieve restaurant-style flavor with this classic French Onion Soup recipe. You will master deeply caramelized onions, create a rich, savory broth, and top it with the signature bubbly Gruyère cheese crust.

Ingredients

Scale
  • 3 lbs yellow onions, thinly sliced
  • 4 tablespoons unsalted butter
  • 1 teaspoon salt, plus more to taste
  • 1/2 teaspoon sugar
  • 1/4 cup dry white wine (optional)
  • 6 cups high-quality beef broth
  • 1 cup water
  • 1 bay leaf
  • 1/2 teaspoon dried thyme
  • 1/4 cup all-purpose flour
  • 1 baguette, sliced 1-inch thick
  • 8 ounces Gruyère cheese, grated
  • 4 ounces Parmesan cheese, grated

Instructions

  1. Melt the butter in a large Dutch oven or heavy-bottomed pot over medium heat. Add the sliced onions, salt, and sugar.
  2. Cook the onions slowly, stirring every 5 to 10 minutes, for 45 to 60 minutes until they are deeply caramelized, dark brown, and sweet. Do not rush this step; this develops the rich flavor.
  3. Sprinkle the flour over the caramelized onions and stir constantly for 2 minutes to cook out the raw flour taste.
  4. If using wine, pour it in and scrape up any browned bits from the bottom of the pot. Cook until the wine has almost evaporated.
  5. Pour in the beef broth and water. Add the bay leaf and thyme. Bring the soup to a simmer, then reduce the heat to low, cover partially, and cook for 30 minutes to allow the flavors to meld. Remove the bay leaf before serving.
  6. Preheat your broiler. Arrange the baguette slices on a baking sheet. Toast them lightly under the broiler for 1 to 2 minutes per side until golden.
  7. Ladle the soup into oven-safe bowls. Place one or two toasted baguette slices on top of the soup in each bowl.
  8. Generously top the bread with a mix of Gruyère and Parmesan cheese.
  9. Place the bowls on a baking sheet and broil for 2 to 4 minutes, watching carefully, until the cheese is melted, bubbly, and golden brown. Serve immediately.

Notes

  • For the deepest flavor, use homemade or low-sodium beef broth.
  • If you skip the wine, add 1/4 cup of water or extra broth when deglazing.
  • Use a sharp knife or mandoline to slice the onions uniformly for even caramelization.
  • Gruyère cheese is essential for the authentic flavor and melt, but you can substitute with Swiss or Provolone if needed.

Nutrition

Find it online: https://alchemychef.com/french-onion-soup-best-classic-recipe/