- 5 pounds sweet onions, thinly sliced (like Vidalia)
- 8 tablespoons unsalted butter
- 2 quarts beef stock, divided
- 2 quarts chicken stock
- Pinch of thyme
- 2-4 teaspoons salt or to taste
- Pepper to taste
- 1/4 cup sherry wine
- 1/4 cup grated Parmesan cheese
- French bread slices, toasted
- Sliced provolone or gruyere cheese
- Sauté onions in butter over medium heat. Carefully and slowly caramelize thoroughly without burning.
- Deglaze the pan with 8 ounces of beef stock. Reduce until gone. Repeat this process until the onions are very dark, even brown.
- Add the remaining beef stock, chicken stock and thyme.
- 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.
- 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.