French Onion Recipe

Prepare onions

Peel and halve the onions, then thinly slice each half into half-moons so you have roughly 2 pounds of sliced onions.

Caramelize onions

In a large heavy-bottomed pot or Dutch oven, heat the butter and 1 tablespoon olive oil over medium heat until butter melts and foams. Add all sliced onions, sprinkle with 1 teaspoon salt and 1 teaspoon sugar. Stir to coat. Cook, stirring every 3–5 minutes, adjusting heat as necessary so the onions soften and begin to brown slowly. This process takes 35–45 minutes: they should become deeply golden-brown and jammy. If edges brown too quickly, lower heat; if they stick, add a splash (1–2 tbsp) of water to deglaze.

Deglaze

When onions are richly caramelized, increase heat to medium-high and add the white wine (if using). Scrape browned bits from the bottom of the pot with a wooden spoon and simmer until the wine has reduced by about half, 2–4 minutes. If not using wine, skip to next step and add a small splash of stock to deglaze.

Build the soup

Add the beef stock, bay leaves, thyme sprigs, Worcestershire sauce, and freshly ground black pepper. Bring to a gentle simmer, reduce heat to low, and simmer uncovered for 20–25 minutes to let flavors meld. Taste and adjust seasoning with additional salt (to taste). Remove thyme sprigs and bay leaves before serving or ladling into bowls.

Prepare crostini

Preheat oven to 375°F (190°C). Brush both sides of baguette slices lightly with 1 tablespoon olive oil and place on a baking sheet. Toast in the oven 8–10 minutes, flipping halfway, until crisp and lightly golden. Alternatively, toast under a broiler for 1–2 minutes per side, watching carefully.

Assemble and gratin

Ladle the hot soup into oven-safe bowls or crocks, leaving about 1/2 inch headspace. Place 1 or 2 toasted baguette slices on top of each bowl (you can float them), then evenly sprinkle about 1/3 cup Gruyère per bowl (adjust to preference) and a light dusting of Parmesan if using. Place bowls on a baking sheet and transfer to a preheated broiler (or oven at 425°F/220°C) until cheese is melted, bubbling, and golden-brown, about 3–6 minutes—watch closely to avoid burning. Alternatively, use a kitchen torch to brown the cheese.

Serve

Carefully remove hot bowls from oven. Let cool a minute, then garnish with a small thyme leaf if desired and serve immediately with a spoon for breaking through the cheese. Enjoy.