French Onion Soup Recipe

Prepare and sweat the onions

Thinly slice the onions into half-moons so you have about 6 cups. In a large heavy-bottomed pot or Dutch oven, heat 1 tablespoon olive oil and 3 tablespoons butter over medium heat until the butter foams. Add all the sliced onions, 1 teaspoon sea salt, and 1 teaspoon sugar (the sugar helps with caramelization). Stir to coat the onions with fat.

Caramelize slowly

Reduce heat to medium-low. Cook the onions, stirring every 3–5 minutes, scraping browned bits from the bottom of the pot. Continue for 35–45 minutes until onions are deep golden-brown and sweet. If they begin to stick or brown too quickly, lower the heat. Do not rush—proper caramelization is key.

Deglaze

Increase heat to medium and add 1 cup dry white wine or dry sherry to the pot to deglaze, scraping up all browned bits. Let the wine reduce by about half, 3–5 minutes, so most of the alcohol cooks off and the flavors concentrate.

Simmer the soup

Add 6 cups beef stock, 1 bay leaf, 3 thyme sprigs, and 1 teaspoon Worcestershire sauce. Bring to a gentle simmer, then reduce heat to low. Simmer uncovered for 20–30 minutes to let flavors meld. Taste and adjust seasoning with additional salt and freshly ground pepper if needed. Remove and discard thyme sprigs and bay leaf before serving.

Prepare baguette toasts

Preheat the oven to 425°F (220°C). Arrange 8 slices of baguette on a baking sheet. Brush lightly with 1 tablespoon olive oil on both sides. Toast in the oven 6–8 minutes until lightly golden, flipping once. When out of the oven, rub the top of each toast with the halved garlic clove for a hint of garlic flavor.

Assemble and melt cheese

Ladle hot soup into oven-safe bowls or crocks, leaving about 1/2 inch headspace. Place 1–2 toasted baguette slices on top of each bowl of soup (or float one big slice). Evenly distribute the 2 cups grated Gruyère over the toasts and soup, and sprinkle the optional 1 tablespoon Parmesan on top. Place the bowls on a baking sheet to catch drips.

Broil until bubbly

Set your oven to broil on high. Place the baking sheet with the bowls on the top rack, about 4–6 inches from the broiler. Broil 2–5 minutes, watching closely, until cheese is melted, bubbling, and lightly browned. Remove carefully — bowls will be very hot.

Finish and serve

Let the bowls sit 2 minutes, then garnish with a small thyme sprig if desired. Serve immediately with an extra spoon and caution about the hot bowl.