Directions

1. Sauté onions in butter over medium heat. Carefully and slowly caramelize thoroughly without burning.
2. Deglaze the pan with 8 ounces of beef stock. Reduce until gone. Repeat this process until the onions are very dark, even brown.
3. Add the remaining beef stock, chicken stock and thyme.
4. Bring to a simmer and cook for 20 minutes to develop flavor. Add salt and pepper, sherry and Parmesan cheese. Taste. Add more salt and pepper if needed.
5. Ladle hot soup into oven-safe bowls, top with slice of French bread and cheese. Place under broiler until the cheese is melted and lightly browned.