Fashion designer Douglas Hannant, the darling of Upper East Side ladies, celebrated the new decade and his cover on Avenue magazine the other night with a dinner in the Oak Room of the Plaza, where he has a shop. Avenue’s Pamela Gross drew the likes of Rudy and Judith Giuliani, who just returned from campaigning in Massachusetts with Scott Brown; Vicky Ward, whose book, “The Devil’s Casino: Friendship, Betrayal and the High Stakes Games Played Inside Lehman Brothers,” will be excerpted in Vanity Fair’s March issue; Countess Nathalie von Bismarck, on her first night out since her split from the count; and Hannant’s partner, Frederick Anderson, who Hannant says “has 500 words for every one word of mine.” Also celebrating was Gross’ husband, Jimmy Finkelstein, whose e5 media company just bought the Hollywood Reporter and Billboard, plus Tinsley Mortimer, Amy Fine Collins, Caryn (Mrs. Jeff) Zucker and Monica Crowley.