Simmering horseradish in cream tempers its pungency; that's the first step in making this distinctive version of mashed potatoes, which nicely complements a sumptuous main course.
Heat the cream and horseradish in a small saucepan over medium heat until just simmering. Remove from heat.
Cover potatoes with cold water in a saucepan. Bring to a boil; add salt. Cook until tender, about 8 minutes; drain.
Force potatoes through a ricer or food mill into a bowl. Stir in butter and the cream mixture. Season with salt.