01 - In a large bowl, combine the chicken pieces with soy sauce, vinegar, ginger-garlic paste, cornstarch, all-purpose flour, black pepper, salt, and egg. Toss until every piece is evenly coated. Allow to marinate for at least 15 minutes.
02 - Heat oil in a deep pan or wok over medium-high heat. Fry the marinated chicken in batches for 3 to 5 minutes per batch until golden and crispy. Transfer to a plate lined with paper towels to drain.
03 - In a large wok or skillet, heat 3 tablespoons of oil over medium-high heat. Add the chopped garlic, green chilies, and diced onion. Sauté for 1 to 2 minutes until fragrant and slightly softened.
04 - Add the diced green and red bell peppers along with the white parts of the spring onions. Stir-fry for about 2 minutes, keeping the vegetables crisp-tender.
05 - In a small bowl, whisk together the soy sauce, chili sauce, tomato ketchup, oyster sauce, sugar, and water until well combined.
06 - Pour the sauce mixture into the wok and bring to a simmer. Add the fried chicken pieces and toss to coat evenly in the sauce.
07 - Pour in the cornstarch slurry and stir quickly. Continue tossing as the sauce thickens and forms a glossy glaze over the chicken and vegetables.
08 - Garnish with reserved spring onion greens. Serve immediately with steamed rice or fried rice.