Bring a large pot of salted water to a boil. Add potatoes and cook until tender but still firm, about 15 minutes. Drain, and let cool. Once cool, peel and grate potatoes.
Melt 3 tablespoons of butter in large nonstick skillet, add a layer of potatoes and a layer of cheese, sprinkle with salt and pepper. Repeat layers. Dot each layer with remaining butter. Sprinkle 2 tablespoons hot water over the top layer, cover and saute at low to medium heat until bottom layer browns. Turn with spatula and brown again.
