Peel potatoes. Uniform size potatoes will cook more evenly. Place in a large saucepan and add cold water to cover by an inch. Bring to a boil over high heat, then switch to medium to low heat and simmer until potatoes are just tender, but not falling apart (about 30 minutes). Drain. Put potatoes back into hot pot for a few minutes to allow the heat of the pot to remove excess moisture.
Mash potatoes with a potato masher. Add melted butter, cream cheese and sour cream. Whip with a hand mixer to smooth consistency. Do not over mix or use a food processor. Add salt and pepper to taste. Transfer to a buttered, 9 x 13 inch casserole.
Bake at 350° for 30 minutes. If made ahead of time, bring to room temperature and reheat at 350° for 20 minutes.
*Perfectly fine to substitute frozen mashed potatoes in this recipe. Cook according to the package and add other ingredients as noted above.