Scrub the potatoes and prick with a fork. Set the microwave to 9 minutes on high and cook the potatoes until tender (you may need a more or less time depending on the size of your potatoes and your microwave).
Cut a slice lengthwise halfway through each potato and add a knob butter to each.
In a bowl mix the cheese and carrot and divide it equally between the potatoes. Place in the microwave for 30 seconds on high, or until cheese is melted and bubbly. Serve immediately.