In a small bowl, whisk together the tamari, honey, rice vinegar, sesame oil, grated ginger, and minced garlic to create the teriyaki base.
Heat a large non-stick skillet over medium-high heat. Add the ground chicken and cook, breaking it apart with a spatula, until browned and cooked through (approximately 7-9 minutes).
Add the diced water chestnuts to the skillet and sauté for 2 minutes to incorporate.
Pour the sauce mixture over the chicken and reduce heat to medium. Simmer for 3 to 5 minutes until the sauce has thickened and glazed the chicken.
Remove from heat and stir in half of the sliced green onions.
Carefully wash and pat dry the lettuce leaves.
Spoon approximately 1/4 cup of the chicken mixture into the center of each lettuce leaf.
Garnish with the remaining green onions and sesame seeds immediately before serving.