Ingredients:
4 large onions, thinly sliced
3 tablespoons butter
2 tablespoons olive oil
4 cups beef broth
2 cups chicken broth
1/2 cup dry white wine (optional)
1 teaspoon Worcestershire sauce
1 teaspoon balsamic vinegar (optional)
Salt and pepper to taste
Baguette or French bread, sliced
Gruyere or Swiss cheese, grated
Fresh thyme or parsley for garnish (optional)
Instructions:
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