Preheat the air fryer to 400ºF.
Begin by adding the cornstarch to a large bowl and remove 1.5 teaspoons of the cornstarch from the bowl and set it aside for later.
Add the garlic powder, salt, ginger, and 1 tablespoon sesame seeds to the cornstarch mixture and whisk to combine. Set aside.
Add the eggs to a separate large bowl and whisk until combined.
Cut the chicken breast into 1-1.5-inch chunks and add the chicken to the bowl with the eggs. Toss the chicken with the egg mixture until the chicken is coated.
Remove the chicken pieces from the egg mixture and allow any excess egg to drip from the chicken.
Add the chicken pieces to the bowl with the cornstarch. Toss the chicken with the cornstarch mixture until the chicken is coated.
Spray the air fryer with cooking spray and then add the coated chicken pieces to the air fryer in one single layer (a few overlaps are ok). Drizzle the chicken with 2 teaspoons of sesame oil.
Air fry the chicken for 10 minutes at 400ºF. When the chicken has cooked for 10 minutes, flip the chicken over and cook it for an additional 6 minutes until golden brown and crispy.
Meanwhile, make the garlic sesame sauce. Add the remaining sesame oil to a small saucepan. When the sesame oil is fragrant add the garlic to the pan.
Sauté the garlic for 2-3 minutes and then add the soy sauce, water, honey, fish sauce, white vinegar, grated onion, and Gochuchang to the pan. Whisk the ingredients together.
Bring the sauce to a boil over medium/high heat and then turn the heat to low and let the sauce simmer for 5 minutes.
Remove ¼ cup of the sauce from the pan and add the remaining 1.5 teaspoons of cornstarch to the ¼ cup of sauce. Whisk the 2 ingredients together. It will thicken. Add it back into the saucepan and whisk the sauce together. Allow the sauce to thicken.
When the chicken is golden brown and cooked through, add the chicken to a large bowl and add then add the sauce. Gently toss the chicken in the sauce until coated.
Garnish the honey sesame chicken with diced green onion and sesame seeds. Serve over rice and enjoy!