Leftover corned beef is something we cherish. They are plenty of recipes on the internet for using up your corned beef: hash, casseroles, colcannon. My favorite is a hearty sandwich with salad on the side.
This is a ciabatta roll spread on both sides with wholegrain mustard, then some (ok, a lot of) grated Irish cheddar, a layer of caramelized onions topped with shredded leftover corned beef. It is heated in a dry pan until the cheddar melts then served quickly so all that gooey cheese is all melted into the corned beef when it’s served. Love this sandwich!