OK, so its not that exciting, but pretty darn good....
Bake as many potatoes as you need for however many people you have
(personally, I like to use white potatoes because I prefer their consistency)
As soon as they're cooked and still very hot, peel them(I usually run them under some water to help get the skin off quickly without burning my fingers)
Toss them in a deep baking dish and mash them down
Chuck in whatever amount of butter makes you feel good
Mash it all down some more
Put in several good healthy spoonfuls of fat free sour cream
Continue mashing to see if you need to add more sour cream
Mix it until its as smooth as you like
Add some salt, pepper, whatever sounds good to you
Grate some white cheddar cheese and add into the mash mix
Bake the whole thing for about 30 minutes or so until the top peaks of the potatoes start to brown slightly
You can sprinkle a little more white cheddar over the top as well if you want