While potatoes are still hot (use oven mitt to hold potato), cut them in half lengthwise. Scoop out the interior flesh of the potato into a medium-sized bowl, leaving a shell about 1/4-inch thick all around. Using a potato masher, mash the potato flesh. Add sour cream and seasonings and mash until smooth, adding a little milk if necessary to make a smooth consistency. Stir in add-ins as desired.
Source: Idaho Potato Commission