Heat vegetable oil in a large skillet over medium-high heat. Add the ground chicken and cook until browned, about 3-5 minutes. Make sure to crumble the chicken as it cooks.
Stir in garlic, onion, hoisin sauce, soy sauce, rice wine vinegar, ginger, and sriracha. Cook and stir until onions have become translucent, about 1-2 minutes.
Stir in water chestnuts and scallions until tender, about 1-2 minutes. Season with salt and pepper, to taste.
Spoon several tablespoons of the chicken mixture into the center of a lettuce leaf, taco-style.
Notes
Customize with additional toppings like shredded carrots or chopped peanuts for added crunch.