Preheat oven 400° (F)
Peel potatoes and place in a large pot of salted water. Bring to a boil, then reduce heat and simmer until tender (about 15-20 minutes). Drain well.
Transfer potatoes into a large bowl and mash well. Fold in cream cheese, seasoning packet, chives, and 3 Tblsp of butter.
Stir in buttermilk just until blended (do not overmix).
Spoon the mashed potato mixture into a lightly greased pie dish. Melt remaining 1 Tblsp of butter and brush the top of the potatoes.
Cover with aluminum foil and bake for 30 minutes. Uncover and bake 15-20 minutes or until pie is a nice golden color.