This French onion soup tastes just like the classic, with plenty of onions and leeks in a rich homemade broth. Here’s how to make it.
INGREDIENTS
2 large yellow onions quartered and thinly sliced
2 red onions quartered and thinly sliced
4 leeks root ends and dark-green tops lopped off, leeks sliced 1/4-inch thin, and washed
1 tablespoon (1/2 oz) unsalted butter
1 tablespoon olive oil
2 tablespoons unbleached all-purpose flour
8 cups vegetable or chicken stock
1 tablespoon Worcestershire sauce [Editor’s Note: or a splash of fortified wine]
1 teaspoon salt
1/2 teaspoon freshly ground black pepper
1 day-old baguette
1/2 cup grated Parmigiano-Reggiano cheese
1/2 cup grated Gruyère cheese (or substitute Comté, Emmentaler, mozzarella, young Manchego, or another melting cheese) plus more as needed
DIRECTIONS
In a large soup pot over medium-high heat, sauté the yellow and red onions and the leeks in the butter and olive oil stirring occasionally to keep the onions from sticking to the bottom of the pot and scorching, until they’ve begun to soften slightly and shrink in volume, 5 to 10 minutes.
Reduce the heat to medium or medium-low and continue to cook the onions for about an hour, until they’re caramel in color and seem practically melted. Keep a careful eye on them, as you don’t want the onions to burn. If it looks like they’re heading in that direction, lower the flame even more, or splash a little bit of water over them to buy you some cooking time.
Sprinkle the properly caramelized onions with the flour, stirring constantly so the flour doesn’t clump. Sauté for another 5 minutes to cook off the floury taste.
Pour the stock over the onions and bring to a boil over high heat. Reduce the heat and simmer for 30 minutes. Stir in the Worcestershire sauce, salt, and pepper. Taste and adjust the seasonings accordingly.
Preheat your oven to 350°F (175°C). Thickly slice the baguette, brush both sides with olive oil, scatter them on a baking sheet, and bake until the bread dries out and the edges are golden brown. Preheat the broiler.
Just before you’re ready to serve the soup, whisk in the Parmigiano-Reggiano. It’s important to whisk in the cheese at the last minute or it will sink to the bottom of the pot and burn. Ladle the warm soup into heatproof bowls or crocks and float a slice of the baked bread in each bowl. Sprinkle some Gruyère over each slice of bread and slide the crocks under the broiler until the cheese bubbles and browns.
