Heat 1 tbsp of avocado oil in a large skillet over medium high heat. Once the pan is hot, add the shishito peppers in a single layer. Cook stirring for 5 minutes, until all sides are blistered. Turn off heat and remove the peppers from the skillet on to plate. Sprinkle with sea salt and set aside.
Cut the chicken into bite-sized pieces and toss evenly with tapioca starch and sea salt. Heat the remaining 3 tbsp of avocado oil in the same skillet over medium heat. Once the pan is hot, add the chicken in a single layer without touching each other (you may need to do this in 2 batches). Fry for 3 minutes on each side until the outer layer is golden and crispy.
Remove the chicken and place the pieces on a paper towel-lined plate. In the same skillet, add garlic, ginger, and crushed red peppers and cook for 1 minute. Add coconut aminos, water, and fish sauce, and stir until combined and simmering. Scrape the bottom of the skillet and simmer for 3-4 minutes, until the sauce is thickened. Add chicken and shishito peppers back into the skillet, and toss with the sauce for 1 minute to coat. Remove from heat and sprinkle with sesame seeds, before serving.