Take your left over corned beef - you had some left over? Why? - dice it into small pieces, mix it with mashed potato and a little chopped parsley.
That's corned beef hash.
Now the fun starts. You can add all sorts of things to it.
Add heaps of butter and beat it until it glistens. Man that hash is sinfully delicious. Add some mustard for a real taste kick.
Add tomato sauce for a reddish hash with a bit of bite. Or worcestershire sauce. Or HP sauce.
Add some boiled cabbage for colcannon-like creation. Or leeks.
Turn it into hash cakes by frying it up in oil or butter. Superb.