In a small bowl, whisk together hoisin sauce, tamari, rice vinegar, Sriracha, and sesame oil. Set aside.
Heat 1 Tablespoon of avocado oil in a large skillet over medium heat. Add diced onions and sauté for 5 minutes until softened. Add garlic and ginger, cooking for 1 more minute until fragrant.
Add the ground chicken to the skillet, breaking it up with a wooden spoon. Cook until fully opaque, about 7-8 minutes.
Pour the sauce over the chicken mixture and stir. Cook for 2 minutes until the liquid reduces slightly. Stir in diced water chestnuts and season with salt and pepper to taste. Remove from heat.
Prepare the peanut sauce by whisking peanut butter, tamari, maple syrup, garlic, and Sriracha together in a small bowl. Add water 1 Tablespoon at a time until the sauce reaches a smooth, pourable consistency.
To serve, spoon about 1/4 cup of the chicken mixture into the center of each lettuce leaf. Top with crushed peanuts and green onions. Drizzle or serve with peanut sauce on the side.