This is a delicious one-dish meal, and it's so easy to prepare. It's a great way to use leftover corned beef, or use canned corned beef in the recipe. The recipe calls for swiss cheese, but a combination of swiss and cheddar or a cheddar jack blend would work as well. The buttery rye bread crumb topping is the perfect finishing touch, and the casserole can be made a day in advance.