Step 1

In a large stockpot or Dutch oven over medium heat, melt the butter. Add onions and cook, stirring frequently, until deeply golden and caramelized. This can take 30-40 minutes; be patient!

Step 2

Add garlic and cook until just fragrant, about 1 minute.

Step 3

Stir in wine, scraping up any browned bits from the bottom of the pan.

Step 4

Stir in beef broth, thyme, and bay leaves. Bring to a boil, then reduce to a simmer and let cook until slightly reduced, stirring occasionally, 15-20 minutes.

Step 5

Discard thyme sprigs and bay leaves, then stir in the sherry and season to taste with salt and pepper.

Step 6

While soup simmers, preheat oven to 400°F. Slice baguette about 3/4-inch thick and arrange slices on a baking sheet in a single layer. Bake until bread is golden and crisp, about 10 minutes.

Step 7

Ladle soup into oven-safe crocks, ramekins, or bowls and place on a baking sheet. Top each soup with a baguette slice (or two or three if using a bigger bowl). Top generously with gruyere.

Step 8

Place under broiler until cheese is melted and golden brown, 2-3 minutes.

Step 9

Serve immediately and enjoy!