Let's start with the sauce. Combine all sauce ingredients in a small bowl. Whisk until the cornstarch dissolves, then set aside.
Now, onto the chicken. Heat sesame oil in a large skillet over medium/high heat. Add mushrooms and sprinkle with salt. Cook for 5-7 minutes until mushrooms release moisture and cook down.
Toss in water chestnuts and sauté for an additional 2 minutes. Remove mushrooms and chestnuts from the skillet and set aside.
Return skillet to heat and add ground chicken. Break it up with a spatula and cook until no longer pink. Stir in soy sauce and cook for 5-6 minutes.
Add mushrooms and water chestnuts back to the skillet. Pour sauce over the mixture and heat over medium/high heat. Let it simmer for 2-3 minutes until thickened.
Once sauce thickens, remove from heat and stir in Thai basil and cilantro. Serve chicken mixture in lettuce wraps and garnish with green onions. Enjoy!