Instructions

1. In a large pot, melt the unsalted butter over medium heat.
2. Add the sliced yellow onions to the pot and cook, stirring occasionally, until they become caramelized and golden brown, about 30-40 minutes. Be patient, as this step is crucial for developing flavor.
3. Once the onions are caramelized, sprinkle the all-purpose flour over them and stir well to coat, cooking for an additional 2 minutes to eliminate any raw flour taste.
4. Pour in the beef broth and dry white wine, stirring to combine all ingredients. Bring the soup to a gentle simmer.
5. Let the soup cook for 20 minutes to allow the flavors to meld together. Season with salt and black pepper to taste.
6. Preheat the oven to 350°F (175°C).
7. Place the sliced baguette on a baking sheet and toast them in the oven until they are lightly golden, about 10 minutes.
8. Ladle the soup into oven-safe bowls, filling them about three-quarters full. Place a few toasted baguette slices on top of each bowl.
9. Generously sprinkle the grated Gruyère cheese over the baguette slices in each bowl.
10. Carefully place the bowls on a baking sheet and broil in the oven until the cheese is melted and bubbly, about 3-5 minutes. Watch closely to avoid burning.
11. Remove the bowls from the oven carefully and let them cool slightly before serving. Enjoy your Soupe à l'Oignon hot!