Heat oven to 350°.
Rub potatoes with shortening for softer skins.
Prick several times with fork to allow steam to escape.
Bake until potatoes are soft, 1 1/4 to 1 1/2 hours.
Cut thin slice from top of each potato; scoop out inside, leaving a thin shell.
Mash potato until no lumps remain.
Add small amounts of milk, beating after.each addition.
(Amount of milk needed to make potato smooth and fluffy depends on kind of potatoes.) Add butter, salt and pepper; beat vigorously until potato is light and fluffy.
Fill potato shells with mashed potato; sprinkle cheese on top.
(To serve immediately, see below.) Wrap, label and freeze.
45 minutes before serving, heat oven to 400°.
Remove Twice Baked Potatoes from freezer and unwrap; place on ungreased baking sheet.
Bake until centers of potatoes are hot, about 40 minutes.
(Or, thaw potatoes uncovered at room temperature 1 hour 45 minutes; bake in 400° oven until golden brown, about 20minutes.)