Put the potatoes in a large saucepan and add enough cold water to cover. Salt the water and bring to a boil over high heat. Reduce the heat and simmer for about 15 minutes, or until the potatoes are tender when pierced with a sharp knife. Drain and return them to the pan.
Set the pan over low heat and cook for about 3 minutes, stirring constantly, until the excess moisture evaporates. Rice the potatoes in a food mill or ricer into a bowl, or simply put them in a bowl and mash them with a potato masher. Add the butter, working it into the potatoes until blended.
In a small saucepan, bring the half-and-half and sliced truffles to a boil over medium heat, infusing the cream with a powerful truffle flavor. Add the mixture to the potatoes slowly, stirring gently, until desired consistency. Do not overmix the potatoes. Season with salt and pepper, cover, and set aside to keep warm.