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 then add 1 teaspoon of salt and reduce the heat and simmer for 15 to 20 minutes, until the potatoes are very tender. 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 and finish them off by stirring in 1/4 cup olive oil.