Producer Randy Jackson is in New York working on fellow “American Idol” Mariah Carey’s new album, and surprised diners at Fresco by Scotto on Saturday night by joining Fox 5 anchor Rosanna Scotto for a holiday dinner at her family-owned restaurant. Jackson joined uber- brander Charlie Walk, NBC’s Hoda Kotb, Gotham magazine editor Samantha Yanks, jewelry designer Jennifer Miler, TV producer Amy Rosenblum, and Soul cycle guru Laurie Cole, among others.