INGREDIENTS :
1 tablespoon unsalted butter 1 tablespoon olive oil 4 large yellow onions sliced in half and cut from pole to pole in no greater than 1/4 inch slices 2 cloves garlic minced 1 teaspoon dried thyme 1/2 cup dry white or red wine (see notes) 3 cups low sodium beef broth or beef stock 1 cup low sodium chicken broth 2 teaspoons Worcestershire Sauce 1 bay leaf Kosher salt and freshly ground pepper to taste Crostini or large croutons 1 cup shredded Gruyère or Swiss cheeseINSTRUCTIONS :
Heat butter and olive oil in a Dutch Oven or stock pot over medium to medium/low heat.
Add the onions and cook for about 45 minutes, stirring every few minutes, until a rich golden brown.
Add the garlic and thyme. Cook for 1 minute.
Add the wine, and using a spoon or spatula, try to remove as much of the brown glazing from the bottom of the pan as possible. Allow the wine to simmer with the onions for about 5 minutes.
Add the chicken broth, beef broth, Worcestershire Sauce, and bay leaf. Simmer for 20 minutes.
Discard the bay leaf and season with kosher salt and fresh ground black pepper to taste.
Add the soup to oven-safe bowls or cups. Top with crostini and grated cheese.
Slip under the broiler for 2-3 minutes.