Baked Onion Apple Cider Soup with Smoked Cheddar Cheese Gratiné
Serves 6 to 8 1 stick unsalted butter 5 medium onions, peeled and thinly sliced 4 cups beef stock 4 cups fresh apple cider 2 teaspoons minced fresh thyme 1/4 cup light brown sugar (omit if cider is sweet enough) Kosher salt and fresh-ground black pepper, to taste Butter as needed for spreading 6 to 8 slices of French bread, 1/2-inch thick 6 to 8 slices of Gruyère or Swiss cheese 2 cups grated smoked Vermont cheddar or traditional cheddar cheese In a large saucepan, melt the butter over medium-low heat. Add the onions and cook until well caramelized, about 20 to 30 minutes, taking care not to burn them. Add the stock, cider and thyme. Bring the soup to a boil, then lower the heat and simmer the soup for 1-1/2 hours. Skim the top of the soup periodically. Season the soup with the brown sugar, if needed, and salt and pepper. The soup may be made up to this point a day ahead and kept covered in the refrigerator. To make the croutons, lightly butter the slices of French bread and broil until toasted on both sides. To serve, preheat the oven to 400°F. Place 6 to 8 ovenproof soup cups or crocks in a large roasting pan and fill them with the hot soup. Pour hot water into the roasting pan to come halfway up the sides of the cups or crocks. Top each cup or crock of soup with a crouton, a slice of Gruyère cheese, and 1/4 to 1/3 cup of grated cheddar. Bake the soup until the cheese is golden brown and the soup is hot and bubbly. Serve immediately.