Soupe à l'Oignon Gratinée

1. In a large heavy-bottomed pot or Dutch oven, melt butter and olive oil over medium-low heat. Add sliced onions and cook slowly for 30-40 minutes, stirring occasionally, until deeply caramelized and golden brown. Sprinkle in sugar to aid caramelization. 2. Add minced garlic and cook for 1 minute until fragrant. Stir in flour and cook for another 2 minutes. 3. Pour in white wine or sherry, scraping up any browned bits from the bottom of the pot. Cook until almost evaporated. 4. Add beef (or vegetable) broth, bay leaf, and thyme. Bring to a simmer, then reduce heat to low, cover, and cook for at least 20 minutes, allowing flavors to meld. 5. Remove bay leaf. Season with salt and pepper to taste. 6. Preheat broiler. Ladle soup into oven-safe crocks or bowls. Place a slice of toasted baguette on top of each bowl, then liberally sprinkle with grated Gruyère cheese. 7. Broil for 2-4 minutes, or until the cheese is bubbling and golden brown. Serve immediately and with caution, as bowls will be hot.