Cut the corned beef against the grain, preferably with a carving knife.
Start assembling the sandwiches by placing 2 pieces of bread down.
Spread 2 tablespoons of the dressing on each piece of bread.
Add several slices of the corned beef.
Add 1 slice of cheese to each sandwich.
In a bowl, combine the sliced cabbage and the apple cider vinegar and mix well.
Divide the cabbage between the 2 sandwiches.
Top each sandwich off with the last piece of bread.
Melt 2 tablespoons of butter in a saucepan over medium heat.
Grill the sandwiches for a couple of minutes until the first side becomes toasted.
Remove the sandwiches and add the last tablespoon of butter to the pan and melt.
Grill the other side of the sandwich until toasted.
You may have to microwave the sandwich a bit if the cheese is not melted.