Ingredients:

  • 3 tablespoons unsalted butter (45g)
  • 2 tablespoons olive oil (30ml)
  • 3 large yellow onions, thinly sliced (about 3 lbs or 1.3kg)
  • 1 teaspoon granulated sugar (5g)
  • 1/2 teaspoon salt (3g)
  • 1/4 teaspoon black pepper (1g)
  • 2 cloves garlic, minced
  • 6 cups beef broth (1.4L)
  • 1 cup dry red wine (e.g., Burgundy or Cabernet Sauvignon) (240ml)
  • 2 tablespoons all-purpose flour (15g)
  • 1 tablespoon Worcestershire sauce (15ml)
  • 1 teaspoon dried thyme (2g)
  • 1 bay leaf
  • 1 baguette, cut into 1-inch slices (about 12 slices)
  • 4 ounces Gruyère cheese, shredded (about 1 cup) (115g)
  • 2 ounces Parmesan cheese, grated (about 1/2 cup) (60g)
  • Fresh parsley, chopped (for garnish)

Instructions:

  1. Melt butter and olive oil in a Dutch oven. Add onions, sugar, salt, and pepper. Cook over medium-low heat, stirring frequently, until deeply golden brown and caramelized (about 25-30 minutes). Add minced garlic during the last minute. Remove from heat.
  2. Sprinkle flour over the caramelized onions and cook for 1 minute, stirring constantly. Gradually whisk in beef broth and red wine, scraping up any browned bits from the bottom of the pot. Add Worcestershire sauce, thyme, and bay leaf. Bring to a simmer, then reduce heat and cook for 15 minutes, stirring occasionally. Remove bay leaf.
  3. Preheat oven to 375°F (190°C). Pour the onion soup mixture into a baking dish. Arrange baguette slices over the soup, overlapping slightly. Top with Gruyère and Parmesan cheeses.
  4. Bake for 25-30 minutes, or until the cheese is melted, bubbly, and golden brown.
  5. Let cool slightly before garnishing with fresh parsley and serving the french onion soup casserole.