What was found
IN FLIGHT, EXPERIENCED STALL WARNING IN FLIGHT, WITH STICK SHAKER, CREW LOWERED FLAPS AND EXTENDED SLATS TO FULL DOWN. AIRCRAFT RETURNED TO MDW AND MADE AN UNEVENTFUL LANDING. INSPECTED AND FOUND AOA VANE BROKEN OFF. REPLACED AOA VANE AND OP CHECKED SYSTEM PER BOEING M/M.