INGREDIENTS
1 tablespoon vegetable oil
4 tablespoons unsalted butter
¾ teaspoon salt
3 pounds Vidalia (or sweet) onions (about 5 medium), halved lengthwise and thinly sliced
¾ teaspoon granulated sugar
½ teaspoon freshly ground black pepper
2 tablespoons all-purpose flour
1 cup dry white wine
1 teaspoon Worcestershire sauce
6 cups beef broth
2 bay leaves
½ teaspoon dried thyme
1 tablespoon dry sherry
1 small baguette, cut into ½-in slices
½ cup grated Parmigiano Reggiano
8 ounces Gruyère cheese, grated (about 2 heaping cups; look for one imported from Switzerland)
INSTRUCTIONS
1. Melt the butter in a large Dutch oven or soup pot over medium heat. Combine the oil, onions, salt, pepper, and sugar in a mixing bowl.
2. Cook, stirring periodically, for 45 to 55 minutes, or until the onions are deep golden brown and caramelized.
3. At first, you’ll simply need to stir the onions every now and then. You’ll need to stir them more frequently as they begin to brown halfway through cooking. Scrape the fond (brown particles) from the bottom of the pan as well.
4. Pour in the wine and turn the heat up to high.
5. Cook, scraping any fond from the bottom of the pan with a wooden spoon, until almost all of the liquid has evaporated and the onions are jammy, 8 to 10 minutes.
6. Stir in the flour.
7. To dissolve the flour, cook for about one minute.
8. In a large pot, combine the broth, Worcestershire sauce, thyme, and bay leaves.
9. Bring to a boil, then reduce to a low heat and cook for about 30 minutes, covered. Taste and adjust seasoning as needed after adding the sherry. Use a few shakes of Worcestershire sauce to give the soup a richer flavor. Add 1/4 teaspoon sugar if it’s not sweet enough.
10. Preheat the oven to 400°F and place an oven rack in the center position while the soup simmers. Arrange the baguette slices on a baking sheet in a single layer.
11. Bake for 10 minutes, or until the bread is dry, crisp, and golden around the edges. Remove from the equation.
12. Heat the broiler by placing an oven rack 6 inches from the element. On a baking sheet, arrange individual broiler-safe crocks and divide the heated soup among them. As the soup will not warm up much in the oven, make sure it is very hot. 1 or 2 baguette pieces on top of each crock (do not overlap slices).
13. Evenly sprinkle with Gruyère and then Parmigiano-Reggiano-Reggiano.
14. Place the crocks in the oven and broil for 3 to 5 minutes, or until the cheese is melted and bubbling around the edges. (Alternatively, if using standard soup bowls, top each toast slice with a slice of cheese and broil for another 2 minutes to melt the cheese.) Serve the soup in bowls with two cheese toasts on top of each serving.)
15. Remove the French onion soup crocks from the oven and set aside to cool for a few minutes before serving.