French Onion Soup Recipe

Prepare onions

Peel and cut the yellow onions in half from root to tip. Place the cut side down and slice thinly into half-moons so you have even, thin slices (about 1/8-inch).

Caramelize onions

In a large, heavy-bottomed pot or Dutch oven, heat 3 tablespoons butter and 1 tablespoon olive oil over medium heat until butter foams. Add the sliced onions, 1 teaspoon salt, 1 teaspoon sugar, and 1 teaspoon freshly ground black pepper. Stir to coat and spread onions evenly. Cook, stirring every 4–5 minutes, adjusting heat as needed to maintain a gentle brown (reduce heat if they start to burn). Continue for 35–45 minutes until onions are deeply golden-brown and jammy.

Deglaze

Increase heat to medium-high and add 1 cup dry white wine (or 1 cup additional stock if not using wine). Scrape the bottom of the pot with a wooden spoon to loosen browned bits (fond). Cook until most of the liquid has evaporated, about 3–4 minutes.

Simmer soup

Add 6 cups beef stock, 2 bay leaves, 3 sprigs fresh thyme, and 1 teaspoon Worcestershire sauce to the pot. Bring to a gentle simmer, then reduce heat to low, partially cover, and simmer for 20–25 minutes to let flavors meld. Taste and adjust seasoning with salt and pepper. Remove and discard thyme stems and bay leaves.

Finish (optional)

If using, stir in 1 tablespoon sherry or brandy off the heat for a bright finish. Keep the soup hot while you prepare the crostini and cheese topping.

Preheat the oven to 425°F (220°C). Slice the baguette on a diagonal into 1/2-inch thick slices. Arrange slices on a baking sheet and brush lightly with 2 tablespoons olive oil on both sides. Toast in the oven for 6–8 minutes until golden and crisp, flipping once. Remove from oven and rub the top of each warm slice with the cut side of 1 garlic clove for subtle garlic flavor.

Portion soup

Ladle the hot soup into oven-safe bowls (ramekins or crocks). Place one or two toasted baguette slices on top of each bowl of soup, depending on bowl size.

Add cheese

Evenly distribute the grated Emmentaler (about 1/2 to 3/4 cup per bowl depending on bowl size) and a sprinkle of Gruyère, covering the bread and creating a thick cheese layer.

Broil until bubbly

Set the oven to broil on high. Place the bowls on a baking sheet and broil 3–5 inches from the element for 2–4 minutes, watching closely, until the cheese is melted, bubbly, and lightly browned. Let cool 2 minutes before serving to avoid burns.

Garnish and serve

Sprinkle each bowl with a little chopped fresh parsley. Serve immediately with any remaining crostini on the side.