Peel the onions and slice them thinly. Thin slices cook evenly and help create the famous caramelized onion flavor.

Place a large pot over medium heat. Add butter and olive oil. Let them melt together until hot.

Add sliced onions to the pot. Stir gently and cook slowly for about twenty minutes until they become soft and golden.

Sprinkle sugar over the onions and add minced garlic. Stir well and cook another two minutes to enhance sweetness.

Add white wine to the pot. Stir and let it cook for two minutes to reduce slightly.

Pour beef broth into the pot. Stir well to combine onions and broth evenly.

Add salt, black pepper, thyme and bay leaf. Mix gently and bring the soup to a gentle simmer.

Let the soup cook for about twenty minutes. This step blends all the flavors together beautifully.

Place French bread slices on a baking sheet. Toast them in the oven until golden and slightly crispy.

Pour the hot soup into oven-safe bowls. Place one toasted bread slice on top of each bowl.

Sprinkle shredded cheese and parmesan over the bread. Make sure the cheese covers the bread evenly.

Place bowls under the oven broiler for two to three minutes until the cheese melts and becomes bubbly.