Directions
Heat 3 tablespoons olive oil in a large heavy-bottomed pot over medium heat. Add the onions and cook, stirring often, for 15–20 minutes until softened.
Add the remaining olive oil and butter. Increase to medium-high and cook for 15 minutes, stirring frequently.
Sprinkle with the sugar and 1 teaspoon salt, then continue cooking for 10–15 minutes until the onions are deeply caramelized.
Stir in the garlic and cook for 1 minute.
Add the wine (or broth) to deglaze the pot, scraping up any browned bits.
Add the beef stock, bay leaves, and thyme. Bring to a simmer, cover, and cook over low heat for 30 minutes.
Remove the bay leaves, season to taste, and stir in the brandy if using.
Toast the French bread at 450°F (230°C) for 5–7 minutes. Top with Gruyère and Parmesan.
Ladle the soup into oven-safe bowls, place the toasted bread on top, add extra cheese, and broil for 3–5 minutes until bubbly and golden.
Serve immediately.
