# Required Ingredients:
→ Alliums
01 - 4 large yellow onions, thinly sliced
02 - 2 large leeks, white and light green parts only, cleaned and thinly sliced
03 - 3 shallots, thinly sliced
04 - 3 garlic cloves, minced
→ Fats
05 - 3 tablespoons unsalted butter
06 - 2 tablespoons olive oil
→ Broth & Umami
07 - 8 cups high-quality beef broth
08 - 1 tablespoon Worcestershire sauce
09 - 2 teaspoons soy sauce
10 - 1/2 cup dry white wine
11 - 2 teaspoons fresh thyme leaves
12 - 1 bay leaf
→ Bread & Cheese
13 - 1 baguette, sliced into 1/2-inch rounds
14 - 2 cups Gruyère cheese, grated
15 - 1/2 cup Parmesan cheese, grated
→ Seasonings
16 - Salt and freshly ground black pepper to taste
# Directions:
01 - In a large heavy-bottomed pot or Dutch oven, heat the butter and olive oil over medium heat until shimmering.
02 - Add the sliced onions, leeks, and shallots. Sauté, stirring frequently, until very soft and deep golden brown, approximately 35 to 40 minutes. Add the minced garlic and cook for 2 minutes more.
03 - Pour the dry white wine into the pot, scraping up any browned bits from the bottom with a wooden spoon to release trapped flavors.
04 - Stir in the beef broth, Worcestershire sauce, soy sauce, thyme, and bay leaf. Bring to a simmer. Reduce heat and cook uncovered for 30 minutes, stirring occasionally.
05 - Season with salt and pepper to taste. Remove and discard the bay leaf.
06 - Preheat the oven broiler. Arrange baguette slices on a baking sheet and toast under the broiler until golden, approximately 1 to 2 minutes per side.
07 - Ladle the hot soup into oven-safe bowls. Top each with toasted baguette slices and a generous amount of Gruyère and Parmesan cheese.
08 - Place bowls under the broiler until the cheese is melted and bubbly, approximately 3 to 5 minutes.
09 - Remove bowls from the broiler and serve immediately, garnished with fresh thyme if desired.
