The Ultimate Cheesy and Spicy Reuben Brats

Name: The Ultimate Cheesy and Spicy Reuben Brats
Ingredients: Three 12-ounce bottles hard apple cider; 1 stick (8 tablespoons) unsalted butter; 1 large onion, sliced; 10 spicy bratwurst; 2 cups sauerkraut, thoroughly drained; 2 teaspoons caraway seeds; 18,000 Island Dressing, recipe follows; 10 New England-style split-top buns, buttered and griddled on the outside; Swiss Cheese Sauce, recipe follows; 1/4 cup sliced chives, for garnish; Thinly sliced Fresno chile peppers, for garnish, optional; 1 cup mayonnaise; 1/4 cup ketchup; 2 tablespoons sliced pickled jalapenos; 1 teaspoon Dijon mustard; 1/4 teaspoon granulated garlic; Kosher salt; One 12-ounce can evaporated milk; 4 ounces Swiss cheese, freshly grated; 1 tablespoon cornstarch; 4 ounces white American cheese, sliced; Kosher salt and freshly ground black pepper