Classic French Onion Soup

Bahan-bahan (4 porsi)

• 4 tablespoons unsalted butter
• 1 tablespoon vegetable oil
• 3 lbs Vidalia ((or sweet onions) (about 5 medium), halved lengthwise and thinly sliced)
• ¾ teaspoon salt
• ½ teaspoon freshly ground black pepper
• ¾ teaspoon granulated sugar
• 1 cup dry white wine
• 2 tablespoons all-purpose flour
• 6 cups beef broth
• 1 teaspoon Worcestershire sauce
• ½ teaspoon dried thyme
• 2 bay leaves
• 1 small baguette, (cut into ½-in (13-mm) slices)
• 1 tablespoon dry sherry
• 8 oz Gruyère cheese (grated (about 2 heaping cups; look for one imported from Switzerland))
• ½ cup grated Parmigiano Reggiano