French Onion Recipe

Prepare onions

Peel and thinly slice enough yellow onions to yield about 6 cups (typically 4–5 medium onions).

In a large, heavy-bottomed pot or Dutch oven set over medium heat, add 1 tablespoon olive oil and 3 tablespoons unsalted butter. When the butter melts and begins to foam, add the sliced onions and 1 teaspoon salt. Stir to coat.

Cook the onions, stirring every 3–5 minutes, for about 25–35 minutes until they are deeply golden brown and caramelized. If they start to stick, lower the heat slightly and scrape the browned bits from the bottom. Sprinkle 1 teaspoon granulated sugar over the onions about 10 minutes into cooking to encourage even browning.

When onions are richly caramelized, sprinkle 1 tablespoon all-purpose flour over them and cook, stirring, for 1–2 minutes to cook the raw flour taste and help thicken the broth slightly.

Deglaze the pot by pouring in 1 cup dry white wine (or sherry), scraping up any browned bits on the bottom with a wooden spoon. Let the wine reduce by half, about 2–3 minutes.

Add 6 cups beef stock, 1 bay leaf, and 2 sprigs fresh thyme. Increase heat to bring the soup to a gentle simmer, then reduce heat to low and simmer uncovered for 20–25 minutes to meld flavors.

Remove and discard the bay leaf and thyme stems. Taste and adjust seasoning with freshly ground black pepper and additional salt if necessary (start with small additions—about 1/4 tsp at a time) before ladling into bowls for finishing.

While the soup simmers, preheat the oven to 400°F (205°C). Arrange baguette slices on a baking sheet and brush lightly with 1 tablespoon olive oil on both sides.

Toast the slices in the oven until golden, about 6–8 minutes, flipping once. As soon as they come out, rub the top of each slice with the cut side of 1 garlic clove to impart a light garlic flavor.

Ladle the hot soup into ovenproof bowls or crocks, leaving about 1/2 inch headspace. Place 1–2 toasted baguette slices on top of each bowl of soup (you can also float them on the surface).

Combine 2 cups grated Gruyère and 1 tablespoon grated Parmesan in a small bowl. Generously mound the cheese mixture over the bread so it covers the bread and a bit of the soup surface.

Place the bowls on a baking sheet and transfer to the oven set to broil (or 500°F/260°C if there is no broil setting). Broil until the cheese is fully melted, bubbling, and deeply golden in spots, about 2–5 minutes — watch closely to prevent burning.

Carefully remove the hot bowls from the oven (use oven mitts). Let cool for 2 minutes, then garnish with a small thyme leaf if desired and serve immediately.