Sour Cream and Onion Mashed Potatoes

Place 5 lb. russet potatoes, peeled, cut into quarters, in a large pot and pour in cold water to cover by 1". Add 1 Tbsp. onion powder and enough kosher salt to make water taste briny like the ocean. Cover and bring to a boil. Reduce heat and simmer (do not boil!) until potatoes are tender but not crumbly, 30–35 minutes (a tester or skewer inserted into centers should meet with very little resistance). Drain potatoes; return to warm pot. Let sit off heat, uncovered, to allow excess liquid to steam off while you heat cream mixture.

Bring 1 cup heavy cream, 2 tsp. freshly ground pepper, 1 tsp. garlic powder, 2 Tbsp. Diamond Crystal or 1 Tbsp. plus ½ tsp. Morton kosher salt, and remaining 2 tsp. onion powder to a simmer in a small saucepan over medium, stirring to dissolve salt, about 5 minutes.

Using a potato masher, smash hot potatoes until smooth (you can also pass through a ricer or food mill into a large bowl if you prefer, then transfer back to pot). Add cream mixture; mix vigorously to combine. Add one 16-oz. container sour cream and 1 cup (2 sticks) unsalted butter, room temperature, and mix again to combine (return pot to low heat if needed). Season with more salt if needed. Stir in 6 scallions (about 1 bunch), dark green parts only, thinly sliced.

Transfer mashed potatoes to a large bowl and top with a pat of unsalted butter and remaining 6 scallions (about 1 bunch), dark green parts only, thinly sliced.