Heat olive oil and butter in a Dutch oven over medium-high heat. Sauté onions and garlic 5 minutes or until tender. Stir in sugar, pepper, and salt. Reduce heat to medium; cook 20 minutes, stirring frequently. Stir in wine, and cook for 1 minute. Add broth and thyme; bring to a boil. Cover, reduce heat, and simmer 2 hours stirring occasionally.
Preheat broiler.
Place bread in a single layer on a baking sheet; broil 2 minutes per side minutes or until toasted. Place 4 ovenproof bowls large baking pan. Ladle 1 cup soup into each bowl. Divide bread evenly among bowls; top each soup bowl with 1/2 cup shredded cheese. Broil 3 minutes or until cheese begins to brown. Let cool 5 minutes before serving and garnish with fresh thyme, if desired.