Caramelized French Onion Soup (Printable version)

Deeply flavored onion broth paired with crispy, cheesy sourdough crostini for cozy dining.

# 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

# Directions:

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; cook, stirring, for 2 minutes to combine.
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.
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 Tips:

01 -
  • The deep umami from slowly caramelized onions tastes like pure comfort, and once you've made it right, you'll crave it on cold evenings.
  • That moment when melted Gruyere meets hot broth creates something almost magical—it's restaurant-quality without leaving your kitchen.
  • One pot and about ninety minutes transforms ordinary ingredients into something that feels like a small celebration.
02 -
  • Don't rush the caramelization; I learned this the hard way and the difference between forty minutes and fifty minutes is the difference between good soup and transcendent soup.
  • The flour is crucial for body and depth, but if you skip it or forget it, your soup will taste thinner and less satisfying.
  • Save good broth for this dish—it's one of those recipes where quality ingredients become almost invisible but their absence screams loudly.
03 -
  • Use a heavy-bottomed pot because it distributes heat evenly and prevents the bottom from burning during that long caramelization—a thin pot will betray you.
  • If you're broiling the crostini in the soup bowls, make sure they're oven-safe and watch that broiler like a hawk; it only takes thirty seconds to go from bubbly to burnt.
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