Boil or steam peeled potatoes cut in 1/3 or 1/2 pieces until tender. I like to use my electric pressure cooker with the potatoes in a steamer basket so they don't get water logged and stay nice and fluffy. (Follow the manufacturers instructions for your pressure cooker)
Drain when done.

In a large bowl, place cream cheese, butter and sour cream. Turn hot, drained potatoes on top. Let sit a few minutes to soften the cream cheese. Mash potatoes then beat with hand mixer adding in garlic salt and pepper.
Turn into buttered casserole dish. Dot with butter and sprinkle with paprika.
Cool then cover with plastic wrap or foil. Refrigerate up to 3 days.
Day of: Bring potatoes to room temperature. Preheat oven 400.
Reheat covered for about 45 minutes, uncover, bake 15 mins more.