Cut chicken into 1-inch pieces and set aside.
Heat oil in a large skillet until hot, but not smoking. Add in onion and garlic and sauté for 2-3 min.
Add chicken to brown for 5-7 minutes, then add coconut aminos. In a small bowl, dissolve the arrowroot starch with water then pour in with ginger, salt, pepper and stir.
Add in sliced cashews and cover skillet with lid to let cook on medium-low heat for another 5-7 minutes.
Serve cashew chicken with toppings and in butter lettuce cups :)