Place your peeled & cubed potatoes in a dutch oven pot and pour cold water just to cover them. Cook at medium to high setting until potatoes are tender but not mushy.
Drain potatoes in a strainer until all water is gone. Place potatoes back in pot and add the butter and sour cream. I use a hand mixer and leave some potato lumps in there (my husband loves them that way) then season with salt and pepper. If the potatoes are too thick you can add a little milk (2% or evaporated is good)