Preheat your air fryer to 375°F (190°C).

Cut the boneless, skinless chicken thighs into 1-2 inch pieces. In a medium bowl, combine the chicken with black pepper, salt, garlic powder, soy sauce, and a beaten egg. Mix well until the chicken is evenly coated. Cover the bowl with plastic wrap or a lid, then refrigerate the chicken for 30 minutes to allow the flavors to combine.

In a small bowl, whisk together soy sauce, brown sugar, rice vinegar, ketchup, and chicken stock. Stir until the ingredients are fully incorporated, then set the bowl aside. This sauce base will be used later to coat the crispy chicken pieces.

Once the chicken has finished marinating, remove it from the refrigerator. Working one piece at a time, coat the chicken thoroughly in cornstarch, ensuring each piece is evenly covered. Place the coated chicken pieces in the air fryer basket in a single layer. If necessary, work in batches to avoid overcrowding. Lightly spray the coated chicken with olive oil or cooking spray. Cook for 8 minutes, then flip the chicken pieces over and spray them again. Continue cooking for another 6-7 minutes until the chicken is golden brown and crispy, with an internal temperature of 165°F (74°C).

In a medium-sized saucepan over medium heat, pour in the sauce base you prepared earlier and bring it to a gentle simmer. In a small bowl, mix the cornstarch with water to create a slurry, then slowly whisk the cornstarch slurry into the simmering sauce. Continue whisking for 1-2 minutes until the sauce thickens to your desired consistency.

Transfer the chicken to a medium size bowl and pour the thickened sauce over the chicken. Gently toss the chicken pieces until they are thoroughly coated with the sauce. Make sure each piece gets a glossy layer of that sweet and spicy goodness. I recommend serving your General Tso's chicken over a bed of white or brown rice and garnishing it with sliced green onions and sesame seeds for added flavor and texture.