Make-Ahead Mashed Potatoes

Place 4 lb. medium Yukon Gold potatoes, scrubbed, in a large pot and pour in cold water to cover by 1". Add a large handful of kosher salt (water should taste briny, like the ocean) and bring to a boil. Reduce heat and simmer until potatoes are very tender but not crumbly, 30–40 minutes. Drain and return potatoes to warm pot to dry (off heat).

Meanwhile, heat ⅔ cup heavy cream and ⅔ cup whole milk in a small saucepan over medium until just about to simmer. Reduce heat to low and keep warm until ready to add to potatoes.

Pass hot potatoes and 1¼ cups (2½ sticks) unsalted butter, cut into pieces, through ricer into a large bowl (this will help combine them quickly; most of the skins should stay behind, but pick out any small pieces that get through if you want); season generously with salt. Mix with a potato masher until butter is melted and combined.

Mixing constantly, gradually add warm cream mixture to mashed potatoes, then mix in ½ cup sour cream. Taste and season with salt and freshly ground black pepper as desired.

Transfer mashed potatoes to a baking dish or other shallow container, let them cool completely, then cover and chill for up to 2 days. To serve, transfer potatoes to a small pot and add ⅓ cup heavy cream and ⅓ cup whole milk; reheat over medium-low, stirring often (but gently) to prevent scorching.