Classic French Onion Soup

Ingredients

• ​1/4 cup extra-virgin olive oil
• 2 tbsp salted butter
• 12 cups vertically sliced onions (about 3 lb/1.5 kg)
• 2 cloves garlic, finely chopped
• 1 tsp granulated sugar
• 1/2 cup dry white wine
• 1/2 cup sherry cooking wine
• 6 cups beef or chicken broth
• 1 bay leaf*
• 1 sprig fresh thyme*
• Salt and freshly ground pepper*
• 12 baguette slices, 1/2 inch (1.25 cm) thick
• 2 cups shredded Swiss cheese
• 2 tbsp freshly grated Parmesan cheese

Directions

1. ​Heat oil and butter in a Dutch oven over medium heat. Add onions, garlic and sugar; reduce heat to medium-low and cook, stirring occasionally, until onions are golden brown, about 40 minutes.
2. Stir in white wine and bring to a boil. Reduce heat and simmer, uncovered, for 5 minutes. Stir in sherry cooking wine and bring to a boil. Reduce heat and simmer, uncovered, for 5 minutes. Add broth, bay leaf and thyme. Bring to a boil. Reduce heat and simmer, uncovered, stirring occasionally, for 1 1/2 hours.
3. Remove and discard bay leaf and thyme. Season to taste with salt and pepper. May be prepared to this point and refrigerated for up to 24 hours.
4. Reheat soup before proceeding. Preheat broiler. Place baguette slices on a rimmed baking sheet. Broil slices until lightly toasted. Remove pan from oven.
5. Ladle soup into ovenproof bowls. For each serving, top with baguette slices, Swiss cheese and Parmesan cheese, dividing equally. Transfer bowls to a rimmed baking sheet. Broil until cheese is melted, bubbly and golden brown.