French Onion Soup

In a large Dutch oven or soup pot, melt the butter over medium heat. Add the oil, onions, salt, pepper, and sugar. Cook, uncovered, stirring occasionally with a wooden spoon, until onions are deep golden brown and caramelized, 45 to 55 minutes.

Add the wine and raise the heat to high. Cook, stirring with a wooden spoon to scrape any fond from the bottom of the pan, until almost all of the liquid has evaporated and the onions are jammy, 8 to 10 minutes.

Add the flour and cook, stirring constantly, for one minute.

Add the broth, Worcestershire sauce, thyme, and bay leaves to the pot. Bring to a boil, reduce the heat to a simmer, and cook, covered, for about 30 minutes.

While the soup simmers, preheat the oven to 400°F and set an oven rack in the middle position. Arrange the baguette slices in a single layer on a baking sheet and bake until the bread is dry, crisp, and golden at edges, about 10 minutes. Set aside.

When the soup is finished, remove the bay leaves and add the sherry; taste and adjust seasoning if necessary.

Adjust an oven rack 6 inches from the broiler element and heat the broiler. Place the oven-proof crocks on a baking sheet. Fill them with very hot soup, top each with 1 or 2 baguette slices without overlapping, and sprinkle evenly with Gruyère and Parmigiano Reggiano. Broil until the cheese is melted and bubbly around the edges, 3 to 5 minutes. Let the crocks cool for a few minutes before serving.