Caramelized French Onion Soup (Printable)

Deeply flavored French onion soup topped with golden cheese crostini for a comforting meal.

# What you'll need:

→ For the Soup

01 - 6 large yellow onions, thinly sliced
02 - 3 tablespoons unsalted butter
03 - 1 tablespoon olive oil
04 - 1 teaspoon sugar
05 - 1 teaspoon salt
06 - 1/2 teaspoon freshly ground black pepper
07 - 2 cloves garlic, minced
08 - 2 tablespoons all-purpose flour
09 - 1/2 cup dry white wine
10 - 6 cups beef broth or vegetable broth for vegetarian option
11 - 2 sprigs fresh thyme or 1/2 teaspoon dried thyme
12 - 1 bay leaf
13 - Salt and pepper to taste

→ For the Sourdough Gruyere Crostini

14 - 1 small sourdough baguette, sliced into 1/2-inch rounds
15 - 2 tablespoons olive oil
16 - 1 cup Gruyere cheese, grated
17 - 1/2 cup Parmesan cheese, grated optional

# Method:

01 - In a large heavy-bottomed pot, melt butter and olive oil over medium heat until fully combined.
02 - Add sliced onions, sugar, salt, and pepper. Cook, stirring frequently, for 35 to 45 minutes until onions are deep golden and caramelized.
03 - Stir in the minced garlic and cook for 1 minute until fragrant.
04 - Sprinkle flour over onions and cook, stirring constantly, for 2 minutes to eliminate the raw flour taste.
05 - Pour in white wine, scraping up any browned bits from the bottom of the pot. Simmer for 2 to 3 minutes to reduce the wine.
06 - Add beef broth, thyme sprigs, and bay leaf. Bring to a gentle boil, then reduce heat and simmer uncovered for 25 to 30 minutes. Adjust seasoning with salt and pepper. Remove and discard thyme sprigs and bay leaf.
07 - While soup simmers, preheat oven to 400°F. Arrange baguette slices on a baking sheet, brush lightly with olive oil, and toast for 5 to 7 minutes until golden.
08 - Top toasted bread slices with grated Gruyere and Parmesan if using. Return to oven and bake until cheese is melted and bubbly, 3 to 4 minutes.
09 - Ladle soup into oven-safe bowls and place crostini on top. Optionally broil for 1 to 2 minutes for additional melting. Serve immediately while hot.

# Expert Advice:

01 -
  • The deep caramel color of the onions tastes like patience paid off, rich and complex in a way that feels restaurant-quality but totally achievable at home.
  • Those cheesy crostini on top deliver a golden, melty contrast that somehow makes the whole dish feel like a celebration.
02 -
  • Don't skip the caramelizing step or try to rush it—those 35–45 minutes aren't a suggestion, they're what transforms ordinary onions into something extraordinary and deeply flavored.
  • Discard the thyme sprigs and bay leaf before serving, or you'll have an unpleasant surprise waiting for someone mid-spoonful, which I learned the embarrassing way.
03 -
  • For vegetarian depth, use vegetable broth and swap half the amount with mushroom broth if you can find it—the umami will make no one miss the beef.
  • A splash of brandy or sherry stirred in just before serving transforms this from comfort to celebration, adding a subtle warmth that rounds everything out.
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