Clean, peel and roughly cube up the potatoes and add to a small pot with cold water.
Add salt and boil until potatoes are tender.
Drain, mash and pour potatoes into a mixing bowl.
Season with salt, sugar and melted butter then add the cornstarch and mix well.
Evenly portion the mixture into 8 balls.
Take a ball, lightly flatten, place a cube of cheese in the middle and wrap the potato around the cheese making sure that the cheese is fully tucked in. Set aside the cheese balls and prepare for dredging with the flour, whisked egg and panko in 3 separate plates.
Dredge the potato balls with flour first, then the egg and lastly the panko and set aside.
In a shallow pan, heat up 1 inch of oil until it reaches about 350 degrees (or until your chopstick bubbles). Fry the balls for about 5 minutes or until golden brown and transfer to a wire rack to drain excess oil.