In a medium stock pot, heat beef broth over medium-high heat.
In a saute pan, add butter and oil and cook over medium-high heat. Once heated, add onions and stir, until onions are tender and transparent. Stir in sugar.
Add onions to heated broth, stir and let simmer for 20 minutes.
Add wine and season with salt and pepper, simmer for 10 minutes.
Pour soup mixture into individual serving bowls and place a slice of bread on top, making sure bread gets well soaked. Place shredded cheese on top of bread and broil, 3 inches below heat, until cheese bubbles.