Classic French Onion Soup: A Comforting Bowl of Rich, Savory Goodness

In a large pot or Dutch oven, heat the butter and olive oil over medium heat. Add the sliced onions, salt, and sugar. Stir frequently for 25-30 minutes, allowing the onions to soften and caramelize. If they start to brown too quickly, lower the heat slightly. This step is key to developing the rich, deep flavor of the soup.
Add Garlic and Wine:

Once the onions are beautifully golden and caramelized, add the minced garlic and cook for another minute until fragrant.
Pour in the white wine, if using, and stir to deglaze the pot, scraping up any flavorful bits from the bottom. Let the wine reduce by half, about 2-3 minutes.
Simmer the Soup:

Add the beef broth, bay leaf, thyme, and black pepper to the pot. Bring the soup to a simmer over medium-low heat, and cook for 30 minutes, stirring occasionally. The flavors will meld together, creating a rich, savory base.
Prepare the Toasted Bread:

While the soup is simmering, preheat your oven to 375°F (190°C). Arrange the baguette slices on a baking sheet and toast them in the oven for about 10 minutes, or until golden and crispy. You can also toast them in a broiler for a quicker result. Set aside.
Assemble and Serve:

Ladle the hot soup into oven-safe bowls. Place a slice of toasted bread on top of each bowl, then generously sprinkle with shredded Gruyère cheese.
Place the bowls under the broiler for 2-3 minutes, or until the cheese is melted and bubbly, with a golden, slightly browned top. Watch carefully to avoid burning the cheese.
Garnish and Serve:

Remove the bowls from the oven (use caution as they will be very hot), and garnish with freshly chopped parsley. Serve immediately.
Serving and Storage Tips: