Peel and cut potatoes into quarters. Boil in water for 10-15 minutes until tender. Drain water and mash potatoes til smooth. Add cream cheese, sour cream, salt, butter and pepper. Beat til fluffy and mixed thoroughly. Pour into greased casserole dish and refrigerate or freeze. Do not add the cheese at this point if you are making them to freeze or refrigerate. If you are making them to use right away; you can sprinkle the cheese on top and bake 5-10 minutes until cheese is melted.
Bake at 350 for 45 minutes uncovered until heated through. Sprinkle cheese (optional) on top and bake an additional 5-10 minutes until cheese is melted.
If you freeze the casserole, double wrap it well with aluminum foil and allow to thaw overnight in the refrigerator before baking. Can freeze up to 3 months.