
Peel the taro and sweet potato, then cut them into 1” (2.5 cm) cubes. Prepare a steamer by boiling 3” (8 cm) water. Place the taro and sweet potato onto a steaming rack and steam until fork-tender, about 15 minutes.
Transfer the steamed taro, sweet potato, butter, sugar and salt into a large bowl and mash with a potato masher or fork until broken down, and the butter and sugar melt. Add the heavy cream. Keep mashing until mostly smooth. Set aside to cool before using.