Drizzle the olive oil in a large frying pan. Break up the chicken into small chunks. Cook over medium heat, continuing to break up the chicken as it cooks. Drain the fat.
Add the garlic and regular onion. Cook for 2-3 minutes.
Add the hoisin sauce, soy sauce, vinegar, and sriracha. Mix throughly and cook for 2-3 minutes.
Add the water chestnuts and green onions. Combine and cook for 2 minutes.
Season with salt and pepper as desired.
Serve immediately on lettuce leaves. Enjoy!