Caramelized French Onion Soup (Printable)

A rich blend of caramelized onions and savory broth crowned with melted Gruyere on toasted sourdough.

# Components:

→ 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
11 - 2 sprigs fresh 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

# Method:

01 - In a large heavy-bottomed pot, melt butter and olive oil over medium heat.
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.
04 - Sprinkle flour over onions and cook, stirring constantly, for 2 minutes.
05 - Pour in white wine, scraping up any browned bits from the bottom. Simmer for 2 to 3 minutes to reduce.
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 degrees Fahrenheit. Arrange baguette slices on a baking sheet, brush with olive oil, and toast for 5 to 7 minutes until golden.
08 - Top toasts with Gruyere and Parmesan cheese. Return to oven and bake until cheese is melted and bubbly, 3 to 4 minutes.
09 - Ladle soup into oven-safe bowls, place crostini on top, and optionally broil for 1 to 2 minutes for extra melt. Serve immediately while hot.

# Expert Advice:

01 -
  • The caramelized onions become so sweet and silky that you'll find yourself eating spoonfuls before the soup even finishes cooking.
  • That crispy, cheese-topped crostini floating on top feels like edible luxury, especially on nights when you need something warm and deeply comforting.
02 -
  • Those 35 to 45 minutes of caramelizing cannot be rushed with high heat—onions need medium heat and patience, or you'll end up with burnt, bitter edges instead of sweet, deep caramel.
  • If your onions seem to stick, add a splash of water rather than oil, which will keep them from burning while they continue their transformation.
03 -
  • Make this soup a day ahead and reheat it gently—the flavors actually deepen overnight as everything melds together, which means day-two soup is sometimes better than day-one.
  • If you're cooking for vegetarians, swap the beef broth for vegetable broth and everything tastes just as rich and satisfying; the onions and cheese do all the heavy lifting.
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