Ingredients

The following ingredients have 7 Servings
  • 2 pounds white onions, thinly sliced
  • 1/4 cup unsalted butter, cut into chunks
  • 4 sprigs fresh thyme
  • 1 teaspoon salt
  • 1/2 cup dry white wine
  • 1 tablespoon flour
  • 1 (32-oz) box of beef broth (see note)
  • 1 bay leaf
  • 1 tablespoon Worcestershire sauce
  • 8 slices French bread (see note), toasted
  • 8 ounces Gruyere cheese, grated

Instruction

  • Place the sliced onions, butter, thyme, and salt into the slow cooker. Toss it all together and then cover and cook on low for 10-12 hours. I stir them a couple of times as they are cooking. Once the onions have cooked discard the thyme sprigs and transfer the onions (and all of the liquid) to a bowl. Cover and refrigerate until you’re ready to make the soup.
  • To make the soup. First, heat the onions and all of their liquid over medium heat in a 5-quart pot. Add the wine and simmer it for a few minutes with the onions. Sprinkle one tablespoon of flour over the top and give it all a stir. Add the beef stock, bay leaf, and Worcestershire sauce to the pot. Raise the heat until the soup is at a strong simmer and then lower the heat to maintain a gentle simmer.
  • Once the soup has simmered for 20 to 30 minutes, check the seasoning and add additional salt, if needed. Ladle the soup into oven-safe bowls.
  • Place bread slices on top of each soup and top each with the grated cheese. Place the bowls on a baking sheet lined with tin foil. Place the bowls under the broiler for a few minutes (keep a close eye on them) until the cheese is melted and bubbly. Remove and serve immediately.