Make Ahead Mashed Potato Casserole

In a large pot, ADD potatoes; COVER with cold water; ADD salt; COVER.

Bring to BOIL over high heat; REDUCE heat to medium-low; SET lid ajar; SIMMER until barely tender (test by piercing with fork), about 20-25 minutes.

DRAIN; COOK over medium-low heat, STIRRING constantly, until potatoes begin to film bottom of pot, about 3 minutes.

ADD cream cheese; using a hand held electric mixer, WHIP until the cheese melts.

ADD sour cream, milk, and softened butter; MIX well; SEASON to taste with salt and pepper.

Into a lightly buttered 13x9 baking dish, TRANSFER potato mixture, smoothing the top; DOT the top of the casserole with the remaining butter; COOL completely.

COVER with plastic wrap and refrigerate (may be done to this point the day before).

REMOVE dish from refrigerator 1 hour before baking.

With oven rack in the center, HEAT oven to 375°.

UNCOVER casserole; BAKE until top is lightly browned and casserole is heated through, about 30 minutes.