Peel potatoes and cut into 2-inch chunks. Place in 5- to 6-quart pan.
Add water to cover, bring to a boil over high heat. Reduce heat to low. Simmer until the potatoes are very tender, about 20 to 25 minutes. Drain and return potatoes to the pan.
Mash potatoes with a potato masher until light and dry. Stir in cheese and milk. Mash until smooth. Add salt and pepper to taste.
Cool potatoes to room temperature. Divide potatoes into 8- to 9-inch oven safe casserole dishes. Cover with foil; freeze.
Reheat covered at 375 degrees, 40 minutes for thawed potatoes, 90 minutes straight from freezer.