Sour Cream Mashed Potatoes Ingredients: 1 1/2 pounds russet potatoes, peeled, cut into 2" pieces 1/2 pound Yukon Gold potatoes, peeled, cut into 2" pieces 1 teaspoon Kosher salt 1/2 cup heavy cream 1/4 cup (1/2 stick) unsalted butter; plus more for serving (optional) 1/2 teaspoon Freshly ground black pepper 1/2 teaspoon garlic powder