Rich French Onion Soup

Preheat your oven to the desired temperature of 325 degrees F (165 degrees C), which is equivalent to a moderate heat level.

In a 4-quart saucepan, melt butter over medium heat until it reaches a liquid state. Add sliced onions and granulated sugar to the saucepan, stirring occasionally as they cook until they turn a golden brown color, approximately 10 minutes.

Stir in flour to combine it with the onions and saucepan juices, ensuring a smooth mixture. Add water, wine, and beef broth to the saucepan, stirring until well incorporated. Bring the mixture to a boil, then reduce the heat to a low setting and cover it with a lid. Allow it to simmer for 10 minutes, creating a rich flavor profile.

Simultaneously, cut four 1-inch-thick slices from the baguette and reserve the remaining bread for serving. Place these toasted baguette slices in the preheated oven and toast them just until they reach a light brown color, approximately 10 minutes. Remove the toasted baguette slices from the oven and set them aside.

Increase the oven temperature to 425 degrees F (220 degrees C), which is a higher heat level.

Ladle the soup into four 12-ounce, oven-safe bowls. Place one toasted baguette slice on top of the soup in each bowl, followed by a layer of Swiss cheese slices. Fit these cheese slices onto the toasted bread slices.

Arrange the soup bowls on a cookie sheet for easier handling and transport.

Bake the soup bowls in the preheated oven just until the cheese is melted, approximately 10 minutes.