French Onion Soup Recipe

Prepare Onions

Peel and halve the yellow onions lengthwise. Slice each half thinly (about 1/8"). You should have roughly 2.5 lbs of sliced onions.

Caramelize Onions

In a large heavy-bottomed pot or Dutch oven, melt 2 tbsp unsalted butter with 1 tbsp olive oil over medium heat. Add the sliced onions, sprinkle with 1 tsp kosher salt and 1 tsp granulated sugar. Cook, stirring frequently, until the onions soften and begin to brown, about 15–20 minutes. Reduce heat to medium-low and continue to cook, stirring every 3–5 minutes, until deeply golden and caramelized, about 25–35 more minutes. If the onions begin to stick, deglaze with a tablespoon of the stock or a splash of water and scrape the fond from the bottom.

Deglaze and Build Flavor

Increase heat to medium and add 1/2 cup dry white wine or sherry. Scrape any browned bits from the bottom of the pot and cook until the wine has mostly evaporated, about 2–3 minutes. Stir in 1 tbsp tomato paste and cook 1 minute to remove raw flavor.

Simmer Soup

Add 8 cups low-sodium chicken stock and 1 cup beef stock (optional for deeper flavor). Add 3 sprigs thyme, 1 bay leaf, and 1 tsp Worcestershire sauce. Bring to a simmer, then lower heat and simmer gently, uncovered, for 20–25 minutes to marry flavors. Taste and adjust seasoning with sea salt and 1/2 tsp freshly ground black pepper (or to taste). Remove and discard thyme sprigs and bay leaf before serving.

Prepare Bread

Preheat oven to 425°F (220°C). Arrange baguette slices on a baking sheet. Brush each slice lightly with the remaining 1 tsp olive oil or a thin smear of butter. Optional: rub each slice with the cut side of a halved garlic clove for a mild garlic note.

Toast and Melt Cheese

Place the baking sheet in the oven and toast slices 5–7 minutes until just golden. Remove from oven, top each slice with a generous layer of grated Monterey Jack (about 2 cups distributed) and a sprinkle of 1/2 cup grated Parmesan and 1/4 tsp freshly ground black pepper. Return to the oven (or place under broiler) and bake until cheese is fully melted and bubbly and edges are golden, 2–4 minutes under broiler or 4–6 minutes in the oven. Watch closely to avoid burning.

Finish Crustini

Remove crustini from the oven and let rest 1–2 minutes so cheese sets slightly. These can be served whole or placed on top of bowls of soup to finish in the oven briefly (see Serving).

Preheat oven broiler (or keep 425°F). Ladle hot soup into ovenproof bowls (or into bowls and transfer to a sheet tray). Float one or two cheese-topped crustini on each bowl of soup. If you prefer the cheese to be melted into the soup further, place bowls on a sheet tray and broil 1–2 minutes until cheese is bubbly and slightly browned. Remove carefully from oven.

Garnish each bowl with a sprinkle of chopped fresh parsley (optional) and a crack of sea salt or freshly ground pepper to taste. Serve immediately, taking care as bowls and melted cheese will be very hot.