Wash the potatoes, peel (optional) and cut into 1" cubes. Place the potatoes in a large pot, add 1 Tablespoon of salt, and add water to cover. Bring to a boil and boil potatoes for 20-30 minutes, or until they are fork-tender.
Drain the water, then add the potatoes back to the pot. Mash potatoes to your desired consistency using a hand masher or potato ricer, then add in your cream cheese, sour cream, milk, butter, salt, pepper, onion powder and garlic powder. Mix until well combined.
Spread the mashed potato mixture into a 9 by 13" casserole dish and let the potatoes cool to room temperature, then cover with plastic wrap and foil and store in the fridge for up to 3 days.
When you're ready to re-heat, preheat oven to 325 degrees. At the same time, remove the potatoes from the fridge to allow the baking dish to come to room temperature (at least 30 minutes).
Just before putting in the oven, remove the plastic wrap, cover with foil and bake for about 30 minutes or until a thermometer reads 160 degrees.
Once your mashed potatoes are warmed through, scoop into a large bowl, add a couple tablespoons of butter and garnish with fresh chopped parsley. Enjoy!