Add some oil to a pan on medium heat along with 1 pound of ground chicken.
Cook until it's reduced and browned and then add the onion, sesame oil, ginger, garlic, rice wine vinegar, hoisin sauce, and soy sauce to taste.
Cook until the sauce thickens, then turn off the heat and add the water chestnuts and green onion.
Stir it in and serve with butter lettuce.