In a 5 quart pot, boil about 2 inches of water. Once boiling, add 1 tablespoon of salt.
While the water is coming to a boil, rinse, peel and dice potatoes into one inch chunks. Place potatoes into boiling water and cover with the lid. (Water should be enough to cover the potatoes). Cook over medium-low heat for 20-25 minutes, or until potatoes are fork tender.
Remove from heat and drain. Place potatoes back into the pan and sprinkle with 1 teaspoon salt. Mash several times with a potato masher.
In a small saucepan, add butter with milk, cream, and 1/4 teaspoon pepper, and place over medium-low heat until butter is melted. Reserve 1/4 cup and set aside. (Or melt in the microwave).
Pour the half of the butter mixture over the mashed potatoes and mix well. Add more of the butter mixture until potatoes are light and fluffy.
Pour potatoes into a greased 9"x13" pan. Cover and refrigerate for up to 24 hours.
When you are ready to bake:
Pour remaining butter mixture over the top of the potatoes (you may need to melt in the microwave). Bake uncovered in a preheated 350 degree oven for 40-45 minutes. Stir before serving, if desired.
*If baking immediately (while potatoes are still hot), reduce baking time.
Notes
This recipe makes 8 generous servings, but will serve anywhere from 8 to 10 people, depending on portion size. If serving a lot of sides such as for Thanksgiving dinner, they could go a little further.
Make sure to chop into evenly-sized chunks for even cooking.
Salt the water generously - this is important as the potatoes will absorb the salt to bring out their flavor.
Don't skip melting the butter and milk together. Cold ingredients will bring down the temperature of the potatoes and you risk them not mashing properly.
Store leftovers in an airtight container in the fridge for 3-4 days or freeze for up to 4 months.
If frozen, thaw completely in the fridge overnight. Reheat in the microwave, or cover with foil and heat in the oven at 375 degrees.