Ingredients:

  • 3 pounds yellow onions, thinly sliced (about 1.36 kg)
  • 4 tablespoons unsalted butter (57g)
  • 2 tablespoons olive oil (30 ml)
  • 1 teaspoon granulated sugar (5g)
  • 1/2 teaspoon kosher salt (3g)
  • 1/4 teaspoon freshly ground black pepper (1g)
  • 1/4 teaspoon dried thyme (1g)
  • 8 cups beef broth, low sodium (approximately 1.9 liters)
  • 1 cup dry red wine (like Cabernet Sauvignon or Merlot) (approximately 240 ml) Optional
  • 2 tablespoons all-purpose flour (15g) Optional, for thickening
  • 2 bay leaves
  • 1 tablespoon balsamic vinegar (15 ml)
  • 1 baguette, sliced into 1-inch thick rounds
  • 2 tablespoons olive oil (30 ml)
  • 6 ounces Gruyère cheese, grated (about 170g)

Instructions:

  1. Melt butter and olive oil in the pot. Add onions, sugar, salt, pepper, and thyme. Cook over medium-low heat, stirring frequently, until deeply golden brown and caramelized (about 45-60 minutes). Watch carefully to prevent burning! If using a skillet, caramelize in batches.
  2. If using, sprinkle flour over the caramelized onions and cook for 1 minute. Deglaze the pot with red wine (if using), scraping up any browned bits from the bottom. Cook until the wine reduces slightly.
  3. Add beef broth, bay leaves, and balsamic vinegar. Bring to a simmer, then reduce heat and simmer for at least 30 minutes to allow the flavors to meld. This is the perfect onion soup recipe.
  4. While the soup simmers, brush baguette slices with olive oil and bake on a baking sheet at 350°F (175°C) until lightly golden and toasted.
  5. Preheat broiler. Ladle soup into oven-safe bowls or ramekins. Top each bowl with a toasted baguette slice and a generous amount of grated Gruyère cheese.
  6. Place bowls under the broiler and broil until the cheese is melted, bubbly, and lightly browned. Watch carefully to avoid burning.
  7. Carefully remove from the oven and serve hot.