Add dipping sauce ingredients to a small saucepan, bring to a low boil over medium heat. Reduce heat and simmer for approximately 4 minutes. Place the dipping sauce in a bowl for serving and set aside.
On medium-high heat add ground chicken to a large skillet or wok, breaking up with a fork as it cooks. Cook until chicken has lost its pink color and is cooked through. Drain off any fat, place cooked chicken in bowl, and set aside.
Add to the same skillet or wok the sesame oil, turn to medium heat and sauté the onion and mushrooms until tender, about 5 minutes. Add garlic and diced water chestnuts, and cook for one additional minute. Add the chicken back in the skillet along with the honey, rice vinegar, and soy sauce. Stir-fry on medium heat for approximately 4-5 minutes, or until ingredients are well combined and heated through.
Prepare lettuce by removing 12 leaves, rinse and pat dry with a paper towel. Place lettuce on serving plates. Equally distribute chicken stir-fry atop lettuce leaves and drizzle with 1-2 teaspoons dipping sauce. Garnish with optional green onions if desired. Allow guests to add additional sauce if they wish. Slightly fold the lettuce wrap while eating.