Classic French Onion Soup with Gruyere Croutons

Melt butter and olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add the sliced onions and cook, stirring occasionally, until they soften and begin to caramelize, about 20-30 minutes. Reduce heat to low if onions begin to burn, ensure even browning and stirring every 5-10 minutes.

Add minced garlic and cook for 1 minute, until fragrant.

Deglaze the pot with dry sherry or white wine, scraping up any browned bits from the bottom. Cook until the liquid is almost completely evaporated, about 2 minutes.

Add beef broth, chicken broth, bay leaf, thyme, and Worcestershire sauce to the pot. Bring to a simmer, then reduce heat and simmer for at least 30 minutes, or up to 1 hour, to allow the flavors to meld.

While the soup simmers, prepare the Gruyere croutons. Preheat oven to 375°F (190°C). Arrange baguette slices on a baking sheet and lightly toast for 5-7 minutes, until lightly golden.

Remove baguette slices from oven and top each with a generous amount of grated Gruyere cheese.

Once the soup has simmered, season with salt and pepper to taste. Remove the bay leaf and thyme sprigs (if using fresh).

Ladle soup into oven-safe bowls. Place 2 Gruyere croutons on top of each bowl of soup.

Place the bowls on a baking sheet and broil in the oven for 2-3 minutes, or until the cheese is melted and bubbly and the croutons are golden brown. Watch carefully to prevent burning.

Let cool slightly before serving. Be careful, the bowls will be hot!