This is called "Make Ahead Potatoes"

If you add sour cream, cream cheese, butter, milk & garlic(optional, but very good), then use a mixer to make them silky smooth, they'll stay moist even after you put any leftovers in the fridge & reheat them another day. It just depends on the amount of potatoes that you've made to how much you add of the other ingredients. For a dutch oven sized pot, I'd use most of a 2 cup container of sour cream, 8 oz chunk (or spreadable tub) of cream cheese, and not quite as much butter & milk as you'd normally use. Even family members who used to hate potatoes will eat more than their share of these spuds!

Mrs. Dirtfarmer