French Onion Soup​ Recipe

Prepare onions

In a large, heavy-bottomed pot or Dutch oven, heat the butter and olive oil over medium heat until butter is melted and foaming.

Add the thinly sliced onions and stir to coat. Cook over medium to medium-low heat, stirring frequently, until onions are very soft and begin to brown, about 25–35 minutes. If they stick, lower the heat and scrape the fond off the bottom with a wooden spoon.

Sprinkle the sugar, 1 teaspoon salt, and 1 teaspoon freshly ground black pepper over the onions to help caramelize. Continue cooking and stirring occasionally until the onions reach a deep golden-brown color, another 10–15 minutes. Total caramelization time should be about 35–50 minutes.

Raise heat to medium-high and add the white wine (or dry sherry). Use a wooden spoon to scrape up any browned bits from the bottom of the pot (deglaze). Let the wine reduce by about half, 2–4 minutes.

Add the veal bone broth, bay leaves, thyme sprigs, and Worcestershire sauce. Stir, bring to a gentle simmer, then reduce heat to low and simmer gently, uncovered, for 20–30 minutes to meld flavors.

Taste and adjust seasoning with coarse sea salt and freshly ground black pepper. If using, stir in 1 tablespoon dry sherry for finishing. Remove and discard thyme sprigs and bay leaves before serving.

While soup simmers, prepare the bread: preheat oven to 400°F (200°C). Arrange bread slices on a baking sheet. Brush both sides lightly with olive oil or melted butter.

Toast the bread in the oven until golden and crisp, about 8–10 minutes, flipping once halfway. If desired, rub the warm toasted bread with the cut side of the garlic clove for a subtle garlic note.

Remove toasted slices and set aside. Prepare the cheese by grating the Swiss (Gruyère/Comté) and mixing with the optional Parmesan.

Ladle the hot soup into oven-safe bowls (or place bowls on a baking sheet). Place one or two toasted bread slices on top of each bowl of soup, then heap 1/3 to 1/2 cup grated Swiss cheese over the bread to fully cover.

Place the bowls under a broiler (or in a very hot oven) just until the cheese is melted, bubbling, and lightly browned, about 2–4 minutes. Watch closely to prevent burning.

Carefully remove bowls from oven using oven mitts. If desired, sprinkle with a little grated Parmesan and finish with a grind of black pepper.

Serve the French onion soup very hot. Provide a spoon and warn diners that bowls and handles can be hot.

Leftover soup (without broiled cheese) can be refrigerated up to 3 days; reheat gently on the stovetop and broil bread with cheese just before serving.