Increase temperature to 350°F. Peel warm potatoes and place in bowl of heavy-duty electric mixer. Beat potatoes until mashed. Add butter, cream, cardamom and nutmeg. Whip until smooth and creamy. Season with salt. Transfer potatoes to 13x9-inch oval baking dish. (Can be made 1 day ahead. Cover and chill. Bring to room temperature before continuing.) Bake potatoes until heated through and beginning to brown on top, about 45 minutes.