I peel and cube the russet potatoes into even-sized pieces, rinse them, then place them in salted water and bring to boil. Once a fork pierces them easily (about 10-15 minutes), I drain and return them to the pot over low heat. I let them steam for about 3 minutes to drive off excess moisture.
I transfer the hot potatoes to a large bowl (or stand mixer), beat them starting on low so they break apart. Then I add the warm melted butter, salt and pepper, followed by cream cheese, and gradually pour in warm half and half until the texture feels creamy but not overly loose.
I grease the baking dish, spread the mashed potatoes evenly inside, then dot the cold butter cubes over the top so they melt into the crust. I bake at 350°F for about 45 minutes until the top is golden and a little crusted while the interior remains creamy.