Prepare all ingredients by mincing garlic, grating ginger, dicing water chestnuts, and slicing green onions (keeping white and green parts separate). Wash and separate butter lettuce leaves and set aside.
Make the sauce by whisking together soy sauce, rice vinegar, hoisin sauce, sesame oil, and sriracha in a small bowl. Set aside.
Heat vegetable oil in a large skillet or wok over medium-high heat until shimmering.
Cook the aromatics by adding minced garlic, grated ginger, and white parts of green onions. Stir constantly for 60 seconds until fragrant.
Add ground chicken to the pan, breaking into small pieces with a spatula. Let cook undisturbed for 2-3 minutes to develop browning, then continue breaking up and cooking until no pink remains (6-8 minutes total).
Add water chestnuts and sauce to the pan. Stir to combine and simmer for 2-3 minutes until sauce thickens and coats the meat.
Remove from heat and stir in green parts of green onions. Taste and adjust seasonings as desired.
Serve immediately by spooning chicken mixture into butter lettuce cups. Garnish with fresh cilantro, sesame seeds, and additional sliced green onions.
