Place the Jerusalem artichokes in a 2-quart saucepan, and cover with water. Set over high heat and bring to a boil. Once the water comes to a boil simmer for 15 minutes, or until easily pierced with a knife. Remove from the heat, drain, and place the Jerusalem artichokes in a food processor with the heavy cream, butter, salt and white pepper. Process for 10 to 15 seconds, or until a smooth puree is formed. Remove from the bowl of the food processor, and place in a heat resistant bowl set over a water bath to keep warm for serving.