Place the potatoes, turnips, carrots, and salt in a Dutch oven, fill with water to cover the vegetables and bring to a boil over high heat.
Reduce the heat to medium-high and boil the vegetables until tender, 20 to 25 minutes. Drain and mash the vegetables with a potato masher. Spoon the mashed vegetables into a serving dish, top with cubes of butter and drizzle with cream.
