3½ pounds Russet potatoes
2 cups heavy cream
8 tablespoons unsalted butter, divided
1½ teaspoons salt
Chives, for serving
Preheat the oven to 450°F and adjust an oven rack to the middle position. Place the potatoes directly on the oven rack. Bake until soft, 50 to 60 minutes.
Remove the potatoes from the oven. While they are still hot, cut each potato in half lengthwise. Using an oven mitt or a folded kitchen towel to hold the hot potatoes, scoop out all of the flesh from each potato half into the bowl. The flesh near the skin gets a little tough, so be sure to leave it behind. Break the cooked potato flesh down into small pieces using a potato masher, fork, or rubber spatula. With stand or hand mixer, eat on low speed until completely smooth and no lumps remain, 1 to 2 minutes, stopping the mixer to scrape down the sides and bottom of the bowl as needed. (Note: it’s important to mash the potatoes while they are still hot, otherwise you’ll end up with lumps.)
Meanwhile, in a small saucepan over medium heat, bring the cream and 6 tablespoons of the butter to a simmer.
Remove the bowl from the mixer stand and, using a large rubber spatula, gradually fold in the hot cream and butter mixture. It will take a few minutes to mix it all in; keep folding until the potatoes are smooth and creamy. Stir in the salt, then taste and adjust seasoning, if necessary. Transfer the mashed potatoes to a large microwave-safe bowl and cover tightly with plastic wrap (the bowl should be large enough that the potatoes don’t touch the plastic wrap). Refrigerate for up to 2 days.
To reheat, use the tip of a knife to poke about 10 holes in the plastic wrap, and microwave at medium-high (75 percent) power until the potatoes are hot, about 14 minutes, stirring halfway through the reheating time. Taste and adjust seasoning, if necessary. Transfer the mashed potatoes to a serving dish, top with the remaining 2 tablespoons of butter, and sprinkle with the chives. Serve hot.
Notes: For perfectly smooth potatoes, pass the potato flesh through a potato ricer before adding them to the mixer.