In a medium bowl, combine the chicken pieces, egg white, 2 tbsp soy sauce, ginger-garlic paste, and black pepper. Mix well to coat the chicken evenly. Let it marinate for at least 15 minutes.

In a separate shallow dish, combine the 1/4 cup cornstarch and 2 tbsp all-purpose flour. Add the marinated chicken pieces and toss until each piece is fully coated. Shake off any excess flour.

Preheat your air fryer to 400°F (200°C). Lightly spray the air fryer basket with cooking oil spray.

Arrange the coated chicken in a single layer in the air fryer basket, ensuring not to overcrowd it (work in batches if necessary). Lightly spray the tops of the chicken with more oil spray.

Air fry for 12-15 minutes, flipping the chicken halfway through, until it is golden brown, crispy, and cooked through. Set the cooked chicken aside.

While the chicken is cooking, prepare the sauce. In a small bowl, whisk together 3 tbsp soy sauce, tomato ketchup, red chili sauce, rice vinegar, sugar, white pepper, and the 1/2 cup of water/broth. Set aside.

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

Add the cubed onion and bell pepper to the wok. Stir-fry for 2-3 minutes until they are slightly tender but still crisp.

Pour the prepared sauce mixture into the wok and bring it to a simmer. Cook for 1-2 minutes, stirring constantly.

Give the cornstarch slurry (1 tbsp cornstarch + 2 tbsp water) a quick stir and pour it into the simmering sauce. Continue to stir until the sauce thickens, which should take about 1 minute.

Add the crispy air-fried chicken to the wok with the thickened sauce. Gently toss everything together until the chicken is well-coated. Be quick to prevent the chicken from losing its crispiness.

Turn off the heat. Garnish with chopped green onions. Serve immediately.