Heat your cast iron skillet (or large skillet or wok) over medium heat for 5 minutes.
When your pan is hot, add the avocado oil. Add in the chopped chicken and season with salt + pepper. Cook, stirring occasionally, for 5-7 minutes until the chicken is cooked through. Remove from the skillet and transfer to a plate.
In the same skillet, add in the chopped celery, bell pepper + green onions. Season with a pinch of salt + pepper. Cook, stirring occasionally, for 5-7 minutes until the vegetables are crisp tender.
Add the chicken back in to the skillet, and pour over the stir fry sauce. Heat for 2-3 minutes. The heat will activate the tapioca starch to thicken the sauce.
Remove from the heat. Add in the chopped cashews. Serve warm over cauliflower rice and garnish with sesame seeds.
Leftovers will keep in an airtight container refrigerated for at least 5 days, or frozen for at least 6 months.