Preheat oven to 350 F. Peel and dice potatoes into 1-inch cubes and place them into a large saucepan. Cover the potatoes with water and bring to a boil over medium heat.
Let potatoes simmer for about 15-20 minutes, or until they are fork tender. Drain the potatoes and place them into a large bowl. Using either a potato masher or a hand mixer, mash potatoes with the butter, salt and pepper. Mash until desired consistency.
Fold in 1 cup of the shredded cheese into the mashed potatoes with a spatula. Spread the potato mixture out into a greased baking dish. Top with the remaining shredded cheddar cheese and bake for 30-35 minutes.
