In a large, covered saucepan, immerse the potatoes in boiling water. Wait until the water returns to boiling and cook potatoes for 15-20 minutes, or until potatoes are tender; drain.
In the bottom of the mixing bowl, add the melted butter and softened cream cheese. Place the drained, hot potatoes on top of the butter and cream cheese. Add the milk, salt, and pepper. Mix on low, building up the speed to medium, and then high, for 4-5 minutes, until nearly smooth.