Preheat oven to 350°. Place chopped apple in a microwave-safe medium bowl; microwave 2-3 minutes until tender, stirring once. Drain if necessary. Stir in next 4 ingredients; set aside. Spread half of the potatoes in a greased 8 x 8 baking pan. Sprinkle with 1 cup cheese. Layer with corned beef mixture; top with remaining potatoes. Garnish with remaining cheese. Bake 25-30 minutes or until casserole is hot and cheese is melted. Makes 6 servings.