Classic French Onion Soup with Cheesy Crouton Topping

Melt the butter with the olive oil in a large heavy-bottomed pot or Dutch oven over medium-low heat. Add the sliced onions and a pinch of salt. Cook slowly, stirring occasionally, for 45-60 minutes, until the onions are deeply golden brown and caramelized. Do not rush this step, it is crucial for flavor.

Add the minced garlic and cook for another 2 minutes until fragrant. Sprinkle the flour over the onions and stir well, cooking for 1 minute to remove the raw flour taste.

Pour in the dry white wine, scraping the bottom of the pot with a wooden spoon to deglaze and release all the flavorful brown bits. Bring to a simmer and cook for 2-3 minutes until the wine has mostly evaporated.

Add the beef broth, bay leaf, and fresh thyme sprigs. Bring the soup to a gentle boil, then reduce the heat to low, cover, and simmer for at least 20 minutes to allow the flavors to meld. Season with salt and freshly ground black pepper to taste. Remove the bay leaf and thyme sprigs before serving.

While the soup simmers, preheat your oven to 200°C (390°F). Arrange the baguette slices on a baking sheet and toast them in the oven for 5-7 minutes, or until lightly golden and crisp.

To serve, ladle the hot soup into oven-safe bowls. Place 1-2 toasted baguette slices on top of each bowl of soup, then generously sprinkle with grated Gruyère cheese.

Place the bowls on a baking sheet and bake in the preheated oven for 10-15 minutes, or until the cheese is melted, bubbly, and golden brown. You can also use the broiler for the last 2-3 minutes for a perfectly gratinéed crust, but watch carefully to prevent burning. Serve immediately.