Warm the cream with the butter in a small saucepan over medium heat until the butter melts; set aside.
Put the potatoes in a medium saucepan with cold water to cover. Bring to boil over high heat. Add 1 teaspoon of salt, then reduce the heat and simmer the potatoes until they are very tender, about 15 to 20 minutes. Drain. Pass the potatoes through a food mill or a ricer into a large mixing bowl. Stir in the warm cream and butter mixture until the cream is absorbed and the mixture is smooth. Season the potatoes with salt and pepper, to taste, and finish by stirring in 1/4 cup of olive oil, if desired.