Preheat the oven to 425º.
Place 6 oven-proof soup crocks onto a cookie sheet. Set aside.
On top of the stove on medium heat, melt the butter in a 4-quart saucepan.
Add in the sugar and onions and sauté it for 5 minutes or until the onions are golden brown.
Whisk in the flour, water, beef broth and wine if you are using it. Cook this until it comes to a boil, then reduce the heat to low. Cover the soup and let it simmer for 10 minutes.
Meanwhile, cut the baguette into 1-inch-thick slices. Toast the slices on the light setting.
Ladle the soup into the soup crocks.
Place 1 or 2 slices of toast on top of the soup.
Fold slices of the cheese over the toast.
Bake at 425º for 10 minutes or until the cheese is melted.
Serve immediately.