WHENEVER NAN and Tommy Kempner were in town, Sunday nights were super-special occasions. Unlike the more formal seated lunches and dinners for 12 to 18 during the week, these Sunday parties were blockbuster sit-all-over-theapartment buffet suppers for 30 to 120 guests, several times a month. The phone would ring and there was Nan: “Do come for a spaghetti dinner,” her tone implying an evening as cozy and relaxed as something any old housewife might slap together for a crowd.