1-First Step: Prepare the Onions Start by melting 4 tablespoons of unsalted butter with 1 tablespoon of vegetable oil in a large soup pot over medium heat. While the butter melts, prepare 3 pounds of Vidalia or sweet onions (about 5 medium) by halving them lengthwise and thinly slicing them. Add the sliced onions to the pot along with ¾ teaspoon salt, ½ teaspoon freshly ground black pepper, and ¾ teaspoon granulated sugar. Cook the onions uncovered, stirring occasionally, until they reach a deep golden brown and are properly caramelized. This process takes 45-55 minutes and is crucial for developing the soup’s signature flavor. Once the onions begin to brown, stir more frequently to scrape the browned bits (fond) from the bottom of the pan. If the onions start to brown too quickly, reduce the heat or add a splash of water to prevent burning.

2-Second Step: Deglaze with Wine Once your onions are deeply caramelized and jammy, add 1 cup of dry white wine to the pot. (Red wine can be substituted if you prefer a different flavor profile.) Increase the heat to high and use your wooden spoon to scrape all the browned bits from the bottom of the pan. Continue cooking until the liquid has completely evaporated and the onions become even more jam-like in consistency, which should take 8-10 minutes. This deglazing step not only prevents anything from burning but also incorporates that flavorful fond back into your soup base.

3-Third Step: Create the Soup Base Stir 2 tablespoons of all-purpose flour into the caramelized onions and cook constantly for about 1 minute. This step is essential as it cooks out the raw flour taste and helps thicken the broth later. Then, gradually add 6 cups of beef broth, 1 teaspoon Worcestershire sauce, ½ teaspoon dried thyme (or 2 tablespoons fresh thyme), and 2 bay leaves. Bring the mixture to a boil, then reduce the heat, cover the pot, and let it simmer for 30 minutes. If you’re interested in more broth-based soup recipes, check out our homemade turkey carcass soup which offers another way to create a rich, flavorful broth.

4-Fourth Step: Prepare the Bread Topping While the soup simmers, heat your oven to 400°F. Take 1 small baguette or sourdough loaf and cut it into ½-inch slices (you’ll need about 16 crostini total). Arrange these slices on a baking sheet in a single layer and bake them until they’re dry, crisp, and golden brown, which should take about 10 minutes. These bread slices will serve as the classic topping for your French onion soup, providing a perfect contrast to the tender caramelized onions.

5-Final Step: Assemble and Serve After the soup has simmered for 30 minutes, remove and discard the bay leaves. Stir in 1 tablespoon of dry sherry and taste the soup, adjusting the seasoning if needed. You might want to add more Worcestershire sauce for umami, a bit more sugar if the onions aren’t sweet enough, or even a splash of balsamic vinegar to brighten the flavors. To finish, set your oven rack 6 inches from the broiler and preheat the broiler. Place oven-safe crocks on a rimmed baking sheet for safety and easier handling. Fill each crock with the hot soup, top with the prepared baguette slices (without overlapping them), and sprinkle generously with 8 ounces of grated Gruyère cheese and ½ cup of grated Parmigiano Reggiano. Place the baking sheet under the broiler and cook until the cheese is melted, bubbly, and lightly browned, which typically takes 3-5 minutes. Remove from the oven, let the soup cool slightly before serving, and enjoy your perfectly prepared classic French onion soup!