Caramelized French Onion Soup (Print Version)

A comforting dish with caramelized onions and cheesy sourdough crostini, perfect for cooler days.

# 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
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

# How-To Steps:

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 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 of the pot. Simmer for 2 to 3 minutes to reduce.
06 - Add beef broth, thyme, 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. Discard thyme sprigs and bay leaf before serving.
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 if using. 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 hot.

# Expert Hints:

01 -
  • The caramelized onions taste like you've unlocked a secret sweetness that was hiding there all along, making every spoonful feel indulgent without being heavy.
  • Those cheesy crostini get crispy on the bottom and gooey on top, adding texture that turns soup into something you actually want to fight for with a spoon.
  • It's one of those dishes that feels fancy enough for guests but simple enough that you're not stressed the whole time you're cooking it.
02 -
  • Don't rush the onions—I learned this the hard way by trying to finish in 25 minutes, which gave me pale onions with a raw bite instead of that silky sweetness that makes the whole dish worthwhile.
  • The flour roux matters more than it seems; skipping it or adding it too early leads to a watery soup that tastes thin, so add it only after the onions are truly caramelized.
03 -
  • A splash of brandy or sherry stirred in just before serving adds luxurious depth that makes people think you've been cooking all day, even if you haven't.
  • Make the soup a day ahead and reheat it gently; the flavors actually deepen overnight, and you'll have less to do when people arrive.
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