Place the peeled, cubed potatoes in a large pot and cover with cold water by at least 2 inches. Add 2 tablespoons of kosher salt to the water. Bring to a boil over high heat, then reduce to a steady medium boil. Cook for 18–22 minutes until the potatoes are completely tender when pierced with a fork — they should fall apart easily.

Drain the potatoes thoroughly in a colander and return them to the empty hot pot. Let them sit over low heat for 1–2 minutes, stirring gently, to evaporate any excess moisture. This step is key for fluffy, non-watery mashed potatoes.

While potatoes drain, gently warm the heavy cream in a small saucepan over low heat until steaming. Melt the butter if not already done. Both should be warm — not cold — when added to the potatoes.

Rice or mash the potatoes while still very hot using a potato ricer, food mill, or hand masher. Work quickly and do not use a hand mixer or stand mixer — over-beating causes gluey potatoes.

Add the softened cream cheese in chunks and stir until fully incorporated. Pour in the warm melted butter and stir through. Add the sour cream and mix gently until smooth.

Pour the warm heavy cream in gradually, stirring between additions, until you reach your desired consistency — creamy and smooth but still holding their shape. Season generously with kosher salt, white pepper, and garlic powder. Taste and adjust seasoning.

Transfer the mashed potatoes to a large airtight container or zip-top bag. Let cool completely at room temperature (no more than 1 hour), then cover tightly and refrigerate for up to 2 days.

To reheat: Spray the insert of a 6-quart slow cooker lightly with non-stick spray. Transfer the cold mashed potatoes into the slow cooker. Add 2–3 tablespoons of warm cream or milk over the top and place a few small pats of butter on the surface. Cover and heat on LOW for 2–3 hours, stirring every 45 minutes and adding splashes of warm cream as needed to reach the desired creamy consistency.

Once heated through and perfectly creamy, switch the slow cooker to WARM for serving. Top with melted butter, fresh chives, cracked black pepper, and flaky sea salt. Serve directly from the slow cooker insert.