Ingredients:

  • 3 lbs (1.36 kg) yellow onions, thinly sliced
  • 4 tablespoons (56g) unsalted butter
  • 2 tablespoons (30 ml) olive oil
  • 1 teaspoon granulated sugar
  • 1/2 teaspoon dried thyme
  • 1/2 teaspoon salt, plus more to taste
  • 1/4 teaspoon black pepper, plus more to taste
  • 8 cups (1.9 L) beef broth (low sodium preferred)
  • 1 cup (240 ml) dry red wine (e.g., Burgundy or Cabernet Sauvignon – optional)
  • 2 tablespoons (30 ml) balsamic vinegar
  • 1 bay leaf
  • 6 slices baguette, cut 1-inch thick
  • 2 tablespoons (30 ml) olive oil
  • 6 ounces (170g) Gruyère cheese, shredded

Instructions:

  1. Melt butter and olive oil in a large pot. Add onions, sugar, salt, and thyme. Cook over medium-low heat, stirring occasionally, until deeply golden brown and caramelized (approx. 45-60 minutes).
  2. If using, pour in the red wine to deglaze, scraping up any browned bits from the bottom of the pot. Cook until the wine is mostly reduced. Add beef broth, balsamic vinegar, and bay leaf. Bring to a simmer, then reduce heat and simmer for 30 minutes. Season with salt and pepper to taste.
  3. Preheat oven to 400°F (200°C). Brush baguette slices with olive oil and bake on a baking sheet for 5-7 minutes per side, or until golden brown and crisp.
  4. Preheat broiler. Ladle soup into oven-safe bowls or ramekins. Top each bowl with a crouton and a generous amount of shredded Gruyère cheese. Place bowls on a baking sheet and broil for 2-3 minutes, or until cheese is melted, bubbly, and lightly browned.
  5. Let cool slightly before serving.