Ingredients:

  • 3 lbs large yellow onions, thinly sliced pole-to-pole
  • 4 tbsp unsalted butter
  • 1 tbsp extra virgin olive oil
  • 1 tsp granulated sugar
  • 0.5 tsp fine sea salt
  • 6 cups low-sodium beef stock
  • 0.5 cup dry sherry
  • 2 cloves garlic, minced
  • 2 sprigs fresh thyme
  • 1 bay leaf
  • 1 tbsp all-purpose flour
  • 1 french baguette, cut into 1-inch thick slices
  • 2.5 cups Gruyere cheese, freshly grated
  • 0.25 cup Parmesan cheese, freshly grated

Instructions:

  1. In a large heavy-bottomed Dutch oven over medium heat, melt the butter and olive oil. Add the sliced onions and stir to coat thoroughly.
  2. Cook onions for 15 minutes until softened. Sprinkle in the sugar and salt. Reduce heat to medium-low and continue cooking for 45-60 minutes, stirring every 5-8 minutes, until onions are deep mahogany and jam-like.
  3. Stir in the minced garlic and cook for 1 minute until fragrant. Sprinkle the flour over the onions and stir for 2 minutes to cook out the raw flour taste.
  4. Deglaze the pot by pouring in the dry sherry, scraping up all the brown bits (fond) from the bottom. Add the beef stock, thyme sprigs, and bay leaf.
  5. Bring to a simmer, then reduce heat and cook for 20 minutes to allow flavors to meld. Remove the thyme sprigs and bay leaf. Season with salt and pepper to taste.
  6. Preheat broiler. Toast baguette slices on a baking sheet until completely dehydrated and golden brown.
  7. Ladle soup into oven-safe crocks. Place a toasted baguette slice on top of each, then generously cover with grated Gruyere and a sprinkle of Parmesan. Broil for 3-5 minutes until the cheese is bubbly and browned.