1Preheat the oven to 450°F and adjust an oven rack to the middle position.
2Prick each potato a few times all over with a fork, then place them directly on the oven rack. Bake until very soft.
3Cut each hot potato in half lengthwise and scoop out the flesh into a stand mixer bowl, leaving the skin behind.
4Break the potato flesh into small pieces using a potato masher, fork, or rubber spatula, then beat on low speed until smooth.
5In a small saucepan over medium heat, bring the cream and 6 tablespoons of butter to a simmer.
6Gradually fold the hot cream and butter mixture into the potatoes using a large rubber spatula until smooth and creamy. Stir in the salt.
7Transfer the mashed potatoes to a large microwave-safe bowl, cover tightly with plastic wrap, and refrigerate for up to 2 days.
8To reheat, poke about 10 holes in the plastic wrap and microwave at 75 percent power until hot. Top with the remaining 2 tablespoons of butter and chives before serving.