Step 1

Melt 2 tablespoons of the butter in a large saucepan over medium-low heat. Add in the onions and season with salt and pepper. Give the onions a stir and allow them to cook, stirring frequently, until softened and starting to brown slightly, about 15 minutes. Turn the heat up to medium, add in the remaining 1 tablespoon butter as well as the maple syrup and allow the onions to cook and caramelize, stirring frequently, for 10 more minutes.

Step 2

Turn the heat to low, add in the garlic, herbes de Provence and bay leaf, if using, and cook for 30 seconds. Carefully deglaze the pan with the brandy and balsamic vinegar, stirring very well and scraping the bottom of the pan to incorporate any of the golden bits that have developed.

Step 3

Add in the wine and simmer until reduced by half, then stir in the beef broth and bring the mixture back to a simmer. Cover the pot and allow it to cook for 25 to 30 minutes to allow the flavors to meld.

Step 4

Meanwhile, toast the bread and cut it into approximately 1-inch cubes.

Step 5

Season the soup with more salt and pepper to taste, then transfer it into an 8- or 9-inch square flameproof baking dish. Scatter the toast cubes over top followed by the cheese.

Step 6

Arrange an oven rack to the middle position and turn your broiler on high. Broil the soup until the cheese has melted and is lightly golden brown, 3 to 5 minutes, making sure to keep your eye on it to ensure it doesn’t burn.

Step 7

Allow to cool slightly before serving.