In a large soup pot, melt the butter and place in oil. Add onions and cook until translucent. Add sugar and flour, cook for 1 minute. Add beef broth, water, salt and pepper. Simmer for 30 minutes. Stir in wines and simmer for 2 hours.
Preheat oven to broil.
To serve, pour soup into soup crocks. Place a piece of French bread on top. Cover bread with grated cheese. Place in oven and broil until cheese is melted and bubbly.