Ingredients:

  • 3 pounds yellow onions, thinly sliced (about 1.36 kg)
  • 4 tablespoons unsalted butter (57 g)
  • 1 tablespoon olive oil (15 ml)
  • 1 teaspoon granulated sugar (4 g)
  • 1/2 teaspoon baking soda (2 g)
  • 1/2 teaspoon dried thyme (1 g)
  • 1/4 teaspoon dried bay leaf (0.5 g)
  • 8 cups beef broth (1.9 liters)
  • 1/2 cup dry sherry or dry white wine (118 ml)
  • Salt and freshly ground black pepper to taste
  • 1 baguette, sliced into ½ inch thick rounds
  • 4 ounces Gruyere cheese, shredded (about 113 g)
  • 2 ounces Parmesan cheese, grated (about 57 g)

Instructions:

  1. Melt butter and olive oil in the Instant Pot using the sauté function. Add onions, sugar, baking soda, thyme, and bay leaf. Sauté, stirring occasionally, until onions are deeply caramelized and golden brown – about 20-25 minutes. The baking soda helps with caramelization.
  2. Pour in sherry or white wine and deglaze the pot, scraping up any browned bits from the bottom. Add beef broth. Seal the Instant Pot lid and cook on high pressure for 15 minutes.
  3. Allow the Instant Pot to naturally release pressure for 15 minutes, then manually release any remaining pressure.
  4. While the soup is cooking, preheat oven to 375°F (190°C). Arrange baguette slices on a baking sheet and bake until lightly toasted, about 5-7 minutes.
  5. Remove bay leaf from the soup. Season with salt and pepper to taste. Ladle soup into oven-safe bowls or ramekins. Top with toasted baguette slices and a generous amount of Gruyere and Parmesan cheese. Broil until cheese is melted and bubbly, about 2-3 minutes. Watch carefully to prevent burning!
  6. Allow to cool slightly before serving and enjoy with a good helping of cheese pulling up with each spoon!