Ingredients

• 4 large yellow onions, thinly sliced
• 4 tablespoons butter
• 2 tablespoons olive oil
• 1 teaspoon sugar
• 1 teaspoon salt
• 2 cloves garlic, minced
• 1/2 cup dry white wine
• 6 cups beef broth
• 2 cups chicken broth
• 2 bay leaves
• 4 sprigs fresh thyme
• 6 slices French bread (1 inch thick)
• 2 cups Gruyere cheese, grated
• 1/2 cup Parmesan cheese, grated
• Black pepper to taste

Instructions

1. In a large Dutch oven, melt butter with olive oil over medium heat. Add the sliced onions and stir to coat with the fat.
2. Cook onions over medium heat, stirring occasionally, for about 15 minutes until they start to soften.
3. Add sugar and salt, then reduce heat to medium-low. Continue cooking for 45 minutes to 1 hour, stirring every 10 minutes, until onions are deep golden brown and caramelized.
4. Add minced garlic and cook for 1 minute until fragrant.
5. Pour in the white wine and scrape up any browned bits from the bottom of the pot. Let the wine reduce by half.
6. Add beef broth, chicken broth, bay leaves, and thyme. Bring to a simmer and cook for 20 minutes. Season with pepper.
7. Preheat your broiler. Toast the bread slices on a baking sheet until golden on both sides.
8. Ladle the soup into oven-safe crocks or bowls. Place a slice of toasted bread on top of each serving.
9. Top generously with Gruyere and Parmesan cheeses.
10. Place bowls on a baking sheet and broil for 2-3 minutes until the cheese is bubbly and golden brown.
11. Let cool for a few minutes before serving - the bowls will be very hot!