Ingredients:

  • 4 large yellow onions, thinly sliced
  • 4 tablespoons unsalted butter
  • 1 teaspoon salt
  • 1 teaspoon sugar
  • 6 cups beef broth
  • 1 cup dry white wine
  • 2 teaspoons fresh thyme leaves or 1 teaspoon dried thyme
  • 1 bay leaf
  • 1 baguette, sliced
  • 2 cups shredded Gruyère cheese

Instructions:

  1. Melt butter in a large skillet over medium heat.
  2. Add sliced onions, salt, and sugar. Sauté until onions are golden and caramelized (approximately 20-30 minutes).
  3. Add caramelized onions, beef broth, wine, thyme, and bay leaf to the slow cooker. Stir to combine.
  4. Cover and cook on low for 6-8 hours or on high for 3-4 hours.
  5. In the last 30 minutes of cooking, preheat your oven to 350°F (175°C). Arrange baguette slices on a baking sheet and toast until golden brown.
  6. Discard the bay leaf from the soup and ladle soup into oven-safe bowls, top with toasted baguette slices, and sprinkle with Gruyère cheese.
  7. Place bowls under the broiler until cheese is bubbly and golden.