Preheat oven to 425°F. Place potatoes in a large pot and cover with cold water. Bring to a boil and add 2 tsp. salt. Boil potatoes until tender when pierced with a knife, about 20 to 25 minutes. Drain.
Transfer potatoes to a large bowl and mash with a masher or potato ricer until smooth and free of lumps. Add cream, butter, egg yolks, 1 tsp. salt and 1/2 tsp. pepper. Mix well.
Line 2 baking sheets with parchment. Spoon potato mixture into a pastry bag fitted with a star tip. Pipe decorative swirled mounds about 2 inches in diameter and about 2 inches apart. Bake until tops are lightly browned, about 20 to 25 minutes.