1. Heat the olive oil in a large skillet over medium-high heat. Add the ground chicken and cook, breaking it up with a spoon, until browned and fully cooked.

2. Stir in the diced onion, garlic, and ginger. Cook for 2 to 3 minutes until fragrant.

3. Add the chopped mushrooms and water chestnuts. Cook for 3 to 4 minutes until slightly softened.

4. In a small bowl, whisk together the soy sauce, hoisin sauce, rice vinegar, sesame oil, brown sugar, and sriracha.

5. In another small bowl, stir together the cornstarch and water until smooth.

6. Pour the sauce into the skillet and stir to coat the chicken mixture evenly.

7. Add the cornstarch slurry and cook for 1 to 2 minutes, stirring, until the sauce thickens and turns glossy.

8. Fold in the sliced green onions.

9. Spoon the warm filling into lettuce leaves and top with sesame seeds or chopped cilantro if desired.

10. Serve immediately.