Fill a large pot with water and bring it to a boil.
Add potatoes and boil until they are fork tender.
Preheat oven to 400°F.
Once potatoes are cooked and have cooled, cut each one in half and cut a small slice off of the rounded end so the potato sits flat.
Scoop out the inside of each potato half saving the potato insides in a bowl.
Add cheese, corned beef, and butter to the bowl with the potato insides.
Salt mixture to taste. Also sprinkle some salt over the potato halves.
Scoop mixture into potato halves and then place them on a baking sheet.
Place baking sheet in oven for 10 minutes.
Remove from oven and serve with a dollop of sour cream.