Prep the Potatoes: Peel and cut the potatoes into 1-inch chunks. Place them in a large pot filled with 6 cups cold water, making sure all the potato pieces are submerged.
Boil the Potatoes: Add 1 tbsp salt to the water. Bring the pot to a boil over high heat, then reduce the heat to medium and simmer for about 15-20 minutes, or until the potatoes are tender when pierced with a fork. Pour into a colander to drain.
Heat the Dairy: While the potatoes are draining, use a medium saucepan to gently heat the heavy cream and butter over low heat. Stir occasionally and remove from heat once the butter is melted. Stir in sour cream or cream cheese plus 1/4 tsp more salt. Keep warm.
Drain and Mash: Once the potatoes are tender, drain them in a colander and return them to the pot. Mash the potatoes using a potato masher or a ricer for an even creamier texture.
Combine: Pour the warm cream and butter mixture over the mashed potatoes, stirring to combine. Season with salt and pepper to taste.
Video
Notes
To keep mashed potatoes warm for a big dinner (or to transport to a potluck), I like to use my Crockpot on the "Keep Warm" setting.