Place potatoes and 1 tablespoon kosher salt into a large pot and cover with water.

Bring to a boil.

Reduce heat to medium-low, cover, and simmer until tender, about 25 to 35 minutes.

Drain the potatoes and transfer them to a large bowl.

Mix half-and-half and butter in a small saucepan over medium-low heat until heated through and butter is melted, about 5 to 10 minutes.

Blend potatoes with an electric hand mixer in the large bowl until mashed.

Slowly pour 3/4 of the cream-butter mixture into the blended potatoes.

Mix on lowest speed until fully incorporated.

Fold in the remaining 1/4 cream-butter mixture and sour cream.

Season with 2 teaspoons kosher salt and black pepper.