In a large mixing bowl, combine the chicken pieces with soy sauce, ginger-garlic paste, black pepper, white vinegar, egg white, and salt. Mix well to ensure every piece is coated. Marinate for at least 15 minutes at room temperature, or up to 30 minutes in the refrigerator.

While the chicken marinates, preheat your air fryer to 400°F (200°C) for 5 minutes.

In a separate shallow bowl, whisk together all-purpose flour, cornstarch, red chili powder, and salt for the coating. Dredge the marinated chicken pieces, a few at a time, into the flour mixture, ensuring they are evenly coated. Shake off any excess.

Lightly spray or brush the air fryer basket with oil. Arrange the coated chicken pieces in a single layer, ensuring not to overcrowd the basket. You may need to cook in batches. Lightly spray the chicken pieces with oil. Air fry for 15-18 minutes, flipping halfway through, until golden brown and cooked through. Internal temperature should reach 165°F (74°C). Set aside.

Heat sesame oil in a large skillet or wok over medium-high heat. Add minced garlic, ginger, and green chilies. Sauté for 30 seconds until fragrant.

Add diced onion, red bell pepper, and green bell pepper. Stir-fry for 2-3 minutes until they are slightly tender-crisp.

Pour in soy sauce, red chili sauce, tomato ketchup, white vinegar, sugar, and black pepper. Stir well to combine. Add 1/4 cup of water or chicken broth and bring the sauce to a gentle simmer.

Whisk the cornstarch slurry once more, then gradually add it to the simmering sauce, stirring constantly until the sauce thickens to your desired consistency.

Add the air-fried chicken pieces to the thickened sauce. Toss gently to coat all the chicken evenly. Cook for another 1-2 minutes, allowing the chicken to absorb the flavors of the sauce.

Garnish with chopped spring onions and toasted sesame seeds. Serve hot with steamed rice or noodles.