In a mixing bowl, combine the chicken pieces, soy sauce, ginger garlic paste, black pepper, egg, cornflour, and salt. Mix well and let rest for 15 minutes.

Heat 1 tablespoon of oil in a skillet over medium-high heat. Add the chicken pieces in a single layer and pan-fry until golden brown and cooked through, reaching an internal temperature of 74°C / 165°F at the thickest piece. Remove and set aside.

In the same pan, add the remaining oil over high heat. Add the minced garlic, ginger, and green chillies, stirring for 30 seconds until fragrant. Add the onion petals and diced bell peppers, tossing briskly for 2 minutes until slightly tender.

Stir in the dark soy sauce, red chilli sauce, tomato ketchup, and vinegar. Pour in the water and bring the mixture to a simmer.

Pour in the cornflour slurry while stirring continuously until the sauce thickens and turns glossy. Return the cooked chicken to the pan, toss until well coated, and remove from heat.