Source: Onion and Fennel Soup Gratin, Barefoot Contessa How Easy Is That?
4 tablespoons (½ stick) unsalted butter
¼ cup good olive oil
3 pounds Spanish onions, halved and sliced ¼ inch thick
2 pounds fennel, tops and cores removed, sliced ¼ inch thick
½ cup good dry sherry
½ cup Cognac or brandy
1 ½ cups good dry white wine, such as Sauvignon Blanc
8 cups canned beef broth
3 bay leaves
1 tablespoon kosher salt
1 ½ teaspoons freshly ground black pepper
1 small sourdough or white French boule, crusts removed, sliced ½ inch thick, and toasted
4 to 6 ounces Gruyère cheese, grated
Heat the butter and oil in a large stockpot over medium-high heat. Add the onions and fennel, and cook over medium heat for 30 to 40 minutes, stirring occasionally, until the onions turn a golden brown. If the onions aren’t browning, turn the heat up. Add the sherry and Cognac, scraping up the brown bits in the pan, and simmer uncovered for 5 minutes. Add the white wine and simmer uncovered for 15 more minutes. Add the beef broth, bay leaves, salt, and pepper, bring to a boil, lower the heat, and simmer uncovered for 20 minutes. Remove the bay leaves and taste for seasoning.
Preheat the broiler and position a rack 5 inches below the heat source. Ladle the soup into heat-proof serving bowls, top with the toasted bread, sprinkle generously with grated Gruyère, and broil for 3 to 5 minutes, until the cheese is melted and bubbly. Serve hot.