Caramelized French Onion Soup (Printable Version)

A rich French onion dish with golden caramelized onions and melted Gruyere on toasted sourdough rounds.

# 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
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

# How To Make It:

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 minced garlic and cook for 1 minute until fragrant.
04 - Sprinkle flour over onions and cook, stirring constantly, for 2 minutes to eliminate raw flour taste.
05 - Pour in white wine, scraping up all browned bits from the pot bottom. Simmer for 2 to 3 minutes to reduce liquid by half.
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 brown.
08 - Remove toasted bread from oven, top each slice with grated 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 additional melting. Serve immediately while hot.

# Expert Advice:

01 -
  • The caramelized onions taste nothing like raw onions—they become naturally sweet and complex in a way that feels almost luxurious.
  • One pot, one simple technique, and suddenly you have restaurant-quality soup that your kitchen smells incredible while making.
  • The toasted crostini with melted Gruyere is the textural contrast that makes every spoonful feel indulgent.
02 -
  • Don't rush the caramelization of the onions by turning up the heat—this is when high heat becomes your enemy because onions will burn instead of slowly turning sweet, and no amount of other ingredients can fix that.
  • If your soup tastes a bit thin or lacks depth after 30 minutes of simmering, it likely needs salt—salt unlocks and intensifies existing flavors in a way that feels almost magical.
03 -
  • Use a heavy-bottomed pot because thin pots create hot spots that can scorch your onions unevenly and ruin the whole batch.
  • If the soup tastes flat, it's almost always a salt issue, not a flavor issue—add salt a teaspoon at a time and taste between additions because salt is the thing that makes all the other flavors sing.
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