Gently pull lettuce leaves off of the head of lettuce. Wash and pat them dry with paper towels. Set aside or chill until ready to serve.
Heat olive oil in a large skillet over medium-high heat. Add ground chicken and cook until browned, breaking up with a wooden spoon or spatula as it cooks; 3-5 minutes. There should not be much, but drain any excess grease or liquid.
Stir in minced garlic, diced onion, Hoisin sauce, soy sauce, rice wine vinegar and grated ginger and cook, stirring frequently, until onions are soft and translucent; 2-3 minutes. Stir in water chestnuts and green onions and cook for an additional 1-2 minutes. Season with freshly ground black pepper as desired to taste. Salt should not be needed but can be added if desired.
To serve, spoon some of the ground chicken mixture into the lettuce cups, garnish with sliced green onions, fold up the sides, and enjoy.
Notes
Serving size: 1/4 cup filling. The recipe allows for 2-3 wraps per person, serving 6-8.