Creating this amazing French Onion Soup is straightforward if you follow these steps:

1. Melt Butter and Oil: In a large pot, melt the butter and olive oil over medium heat.
2. Caramelize Onions: Add the sliced onions and sugar, stirring occasionally. Cook for about 30-40 minutes until the onions are soft and caramelized.
3. Add Broth and Wine: Once the onions are caramelized, stir in the beef broth, white wine (if using), thyme, bay leaf, salt, and pepper.
4. Simmer: Bring the soup to a simmer, then reduce the heat and let it simmer for about 30 minutes. Taste and adjust seasoning as desired.
5. Prepare Bread: While the soup simmers, preheat your oven to 350°F (175°C). Arrange the bread slices on a baking sheet and toast them in the oven until golden brown, about 10 minutes.
6. Remove Bay Leaf: After the soup has simmered, remove the bay leaf and discard it.
7. Serve Soup: Ladle the soup into oven-safe bowls, filling them about three-quarters full.
8. Add Bread and Cheese: Place a slice of toasted bread on top of each bowl of soup. Sprinkle generously with Gruyère and Parmesan cheese.
9. Broil: Place the bowls on a baking sheet and broil in the oven until the cheese is bubbly and golden, about 3-5 minutes. Keep a close eye on them to prevent burning.
10. Garnish and Serve: Remove from the oven and let cool slightly before serving. Garnish with additional thyme if desired.

These steps will guide you in creating this incredible French Onion Soup effortlessly.