French Onion Soup

1.Begin the caramelization process: In a large, heavy-bottomed pot or Dutch oven, melt the butter and olive oil over medium-low heat. Add the sliced onions and the granulated sugar (if using).

2.Cook the onions slowly: Stirring frequently, cook the onions for 45 to 60 minutes. The goal is a deep, rich, golden-brown color and a jam-like texture. If the onions start to stick or burn, reduce the heat immediately. This slow caramelization is crucial for the soup's flavor.

3.Deglaze and thicken: Once caramelized, season the onions with 1 teaspoon of salt and 1/2 teaspoon of pepper. Increase the heat to medium. Pour in the white wine and scrape up any browned bits (fond) from the bottom of the pot. Cook until the wine has almost completely evaporated (about 5 minutes). Sprinkle the flour over the onions and stir well for 1 minute.

4.Simmer the soup: Pour in the beef stock, add the bay leaf and the thyme bundle. Bring the soup to a simmer, then reduce the heat to low, cover partially, and cook for at least 30 minutes to allow the flavors to fully meld. Remove the bay leaf and thyme bundle before serving.

5.Prepare the croutons: While the soup simmers, preheat the oven broiler. Arrange the baguette slices on a baking sheet. Toast them under the broiler for 2-3 minutes per side until golden brown and crisp. Set aside.

6.Assemble and broil: Taste the soup and adjust seasoning if necessary. Ladle the hot soup into oven-safe crocks or bowls. Place 2-3 toasted baguette slices on top of the soup in each bowl. Generously cover the bread and the edges of the bowl with grated Gruyère cheese.

7.Gratinate: Place the crocks on a baking sheet and broil on the top rack for 2-4 minutes, watching carefully, until the cheese is melted, bubbly, and deeply golden brown. Serve immediately, warning guests that the bowls are extremely hot.