Place the potatoes in a large pot and cover with cold water. Add a tablespoon of salt and bring to a boil over medium-high heat. Boil until fork-tender, about 15 to 20 minutes. Drain well. Press the potatoes through a potato ricer back into the pot.
Meanwhile, in a small saucepan, combine the milk with 6 tablespoons of the butter and cook over medium heat until the butter melts.
Place the pot back over low heat and pour the hot milk mixture over the riced potatoes, stir until combined, about 2 minutes. Add the remaining 2 tablespoons of butter, then gradually add the crème fraîche. Stirring frequently, cook until the potatoes are warmed through, about 5 minutes.
Season with salt and pepper. Transfer the mashed potatoes to a warmed bowl and serve immediately.