French Onion Soup Recipe

Prepare onions

Heat a large heavy-bottomed pot or Dutch oven over medium heat. Add the butter and olive oil and let the butter melt but not brown.

Add the thinly sliced onions, spread them evenly in the pot, and cook, stirring every few minutes, until they begin to soften, about 10 minutes.

Sprinkle the sugar and salt over the onions to help with caramelization. Continue to cook the onions over medium-low heat, stirring frequently and scraping browned bits from the bottom, until the onions are deep golden brown and sweet, 35–45 minutes. Adjust heat as needed to prevent burning.

When the onions are richly caramelized, add the freshly ground black pepper and deglaze the pot with the dry white wine (if using). Scrape any fond from the bottom and simmer until the wine is almost evaporated, about 2–3 minutes.

Add the veal stock and chicken stock to the pot. Stir in the thyme sprigs, bay leaves, and Worcestershire sauce. Bring the soup to a gentle simmer, then reduce heat to low and simmer uncovered for 20–25 minutes to meld flavors.

Taste and adjust seasoning with additional salt and pepper as needed. Remove and discard thyme sprigs and bay leaves before serving.

While the soup simmers, preheat the oven to 450°F (230°C) or set your broiler to high. Arrange baguette slices on a baking sheet, brush each side lightly with olive oil, and toast until golden, about 5–7 minutes, flipping once. If using garlic, rub the toasted side lightly with the halved garlic clove for a hint of flavor.

Ladle the hot soup into ovenproof bowls or crocks, filling each about three-quarters full. Place 1–2 toasted baguette slices on top of each bowl of soup (you can push them slightly into the soup so they soak a little).

Mix the Gruyère and provolone together (reserve a little for finishing). Heap a generous amount of the cheese mixture over the bread so it covers the bread and overlaps the rim slightly.

Place the bowls on a baking sheet and transfer to the oven. Broil or bake until the cheese is fully melted, bubbly, and beginning to brown in spots, 3–6 minutes — watch carefully to avoid burning.

Remove from oven, let cool 1–2 minutes, garnish with chopped parsley, and serve hot. Optionally pass extra grated cheese at the table.