In a large skillet, cook pork and onion over medium heat 6-8 minutes or until pork is no longer pink and onion is tender, breaking up pork into crumbles.
Stir in hoisin sauce, garlic, ginger, vinegar, soy sauce and chili sauce until blended. Add water chestnuts, green onions and oil; heat through. To serve, place pork mixture in lettuce leaves; fold lettuce over filling.
