Making Dutch Oven French Onion Soup is straightforward if you follow these steps:

1. Preheat the Oven: If you plan to broil the cheese at the end, preheat your oven to 450°F (232°C).
2. Melt Butter and Oil: In a large Dutch oven, heat the butter and olive oil over medium heat until melted.
3. Add Onions: Add the sliced onions and sprinkle with salt. Stir to coat the onions in the butter and oil.
4. Caramelize Onions: Cook the onions, stirring occasionally, for about 30-40 minutes until they become soft and caramelized, turning a rich golden brown. Add the sugar halfway to help with caramelization.
5. Add Garlic: Stir in the minced garlic and cook for an additional 1-2 minutes until fragrant.
6. Deglaze the Pot: Pour in the white wine (if using) and scrape the bottom of the pot to release any flavorful brown bits. Allow it to simmer for about 5 minutes.
7. Add Broth and Herbs: Pour in the beef broth, thyme, and bay leaves. Bring the mixture to a simmer and let it cook for about 30 minutes, uncovered.
8. Season: Taste and adjust seasoning with salt and freshly cracked black pepper.
9. Prepare the Bread: While the soup simmers, slice the French baguette and place the slices on a baking sheet. Toast in the oven for 5-10 minutes until golden brown.
10. Add Cheese: Remove the bay leaves from the soup. Ladle the soup into oven-safe bowls, top with toasted bread slices, and layer on the Gruyère and mozzarella cheeses.
11. Broil: Place the bowls under the broiler for about 3-5 minutes or until the cheese is bubbly and golden brown.
12. Garnish and Serve: Remove from the oven, let cool slightly, and garnish with chopped parsley before serving.

Following these steps will lead you to a delicious Dutch Oven French Onion Soup that’s sure to impress anyone lucky enough to share it with you.