Combine stir-fry sauce, sherry and cornstarch; set aside. In rondo or large sauté pan, stir-fry pork, onion and garlic over high heat until pork is no linger pink, stirring and breaking up pork with spoon or flat spatula; drain off fat.
Add stir-fry sauce mixture; cook, stirring, until pork is evenly coated with sauce. Remove from heat; stir in cilantro and sesame oil. Divide meat mixture equally among lettuce leaves and wrap to enclose.