Classic French Onion Soup Gratinée

Caramelize Onions

1. 1In a large heavy-bottomed pot or Dutch oven, melt butter and olive oil over medium heat.
2. 2Add sliced onions and cook slowly, stirring occasionally, until deeply caramelized and sweet, about 45-60 minutes.
3. 3Add minced garlic and thyme, cook for another minute until fragrant.

Simmer Soup

1. 1Pour in cognac or brandy, scraping up any browned bits from the bottom of the pot. Let it bubble and reduce slightly for 2 minutes.
2. 2Add beef broth and bay leaf. Bring to a simmer, then reduce heat to low, cover, and cook for at least 30 minutes to allow flavors to meld.
3. 3Remove bay leaf. Season soup with salt and pepper to taste.

Prepare Topping

1. 1While soup simmers, preheat your broiler. Arrange baguette slices on a baking sheet and toast until golden brown on both sides.
2. 2In a small bowl, combine Gruyère and Parmesan cheese.

Gratinée

1. 1Ladle hot soup into oven-safe bowls or crocks.
2. 2Top each bowl with one or two baguette slices.
3. 3Generously sprinkle the cheese mixture over the baguette slices, ensuring they are well covered.
4. 4Place bowls on a baking sheet and broil for 2-4 minutes, or until cheese is melted, bubbly, and lightly browned. Watch carefully to prevent burning.