In a bowl, whisk soy sauce, hoisin, sesame oil, rice vinegar, peanut butter, honey, chili sauce, garlic powder, and ginger. Set aside.
Heat peanut oil in a skillet or wok over medium-high heat. Sauté onion and garlic until fragrant.
Add ground chicken and cook until browned and fully cooked, breaking it into small pieces.
Stir in bell pepper and water chestnuts. Cook for 3–4 minutes until slightly softened.
Pour in the sauce and simmer for 2 minutes until glossy and well-coated.
Spoon the mixture into lettuce leaves. Garnish with peanuts and green onions before serving.