Scrub and peel potatoes. Place them in a large saucepan and cover with water. Cook over medium-high heat until tender, about 15-20 minutes. Cool potatoes for 10-15 minutes. Place in a lightly greased 9" x 13" baking dish and mash with fork. (Or use prepared mashed potatoes.)
In a bowl, combine the remaining ingredients except cheese; stir to combine. Spread over potatoes and top with cheese.
Bake, uncovered, at 350 degrees for about 30 minutes, until bubbly and cheese is melted.