Place potatoes in a large stockpot and add enough water to cover potatoes.
Bring water to a boil, cover with lid, and reduce heat to medium and let cook for about 20-25 minutes or until potatoes are fork-tender. Drain the water.
If preferred, peel the potatoes (I usually just leave the peels on). Put the cooked potatoes in a large bowl and mash with a potato masher.
Mix in butter, cream cheese, sour cream, milk, and salt until completely combined.
Spray a 9 x 13 inch baking pan with non-stick cooking spray. Scoop mashed potatoes into the prepared pan.
If desired, brush the top of the potatoes with additional melted butter, fresh parsley, and paprika.
If you are making these mashed potatoes for later, cover the potatoes and refrigerate (these are fine made up to 24 hours in advance).
When you are ready to bake these mashed potatoes, let the potatoes sit at room temperature for about 30 minutes before putting them in the oven.
Preheat oven to 350 degrees and bake uncovered for about 25-30 minutes or until the potatoes are heated all the way through.