Ingredients:

  • 3 lbs yellow onions, thinly sliced
  • 3 tbsp unsalted butter, cubed
  • 1 tsp granulated sugar
  • 1 tsp kosher salt
  • 6 cups beef bone broth
  • 0.5 cup dry Sherry or white wine
  • 2 tsp Worcestershire sauce
  • 3 sprigs fresh thyme
  • 1 large bay leaf
  • 0.5 tsp black pepper, freshly cracked
  • 1 large French baguette, cut into 1-inch thick slices
  • 2 cups Gruyère cheese, freshly grated
  • 0.5 cup Provolone cheese, freshly grated

Instructions:

  1. Peel and slice the onions into uniform 1/4-inch half-moons using a mandoline or sharp knife.
  2. Place the onions in the slow cooker and toss thoroughly with the cubed butter, salt, and sugar.
  3. Cover and cook on LOW for 8 to 10 hours (ideally overnight). Do not open the lid during this process to ensure consistent caramelization.
  4. Once onions are dark mahogany and jammy, pour in the beef stock, wine, and Worcestershire sauce. Add thyme sprigs, bay leaf, and black pepper.
  5. Cover and continue cooking on LOW for another hour to allow flavors to meld.
  6. Ladle soup into oven-safe crocks. Top each with a slice of toasted baguette and a generous mixture of Gruyère and Provolone.
  7. Place crocks on a baking sheet and broil for 2-3 minutes until the cheese is bubbly and browned.