Step 1

Peel and cut 3 pounds russet potatoes into 1 1/2-inch chunks. Place in a large saucepan or pot and add enough cold water to cover by about 1 inch. Add 1 tablespoon of the kosher salt and bring to a boil over medium-high heat. Reduce the heat to maintain a simmer and cook until the potatoes are knife tender, about 15 minutes.

Step 2

Drain the potatoes in a colander. Add 1 1/3 cups whole or 2% milk, 4 tablespoons unsalted butter, and the remaining 2 teaspoons kosher salt to the now-empty pot. Place over medium-low heat, stirring occasionally, until the butter is melted.

Step 3

Pass the potatoes through a ricer into the pot, or return the potatoes to the pot and mash with a potato masher until desired consistency. Gently stir to combine. Add 1/2 cup sour cream and gently stir until combined. Taste and season with more kosher salt as needed. Transfer to a serving bowl and garnish with 1 tablespoon finely chopped fresh chives or scallion greens if desired.