Marinate the Chicken: In a bowl, mix chicken with cornflour, all-purpose flour, salt, pepper, and egg. Let it marinate for at least 20 minutes.
Fry the Chicken: Heat oil in a skillet over medium-high heat. Fry chicken in batches for 4-5 minutes until golden and crispy. Remove and set aside.
Prepare the Sauce: In the same pan, add 1 tablespoon oil. Sauté ginger-garlic paste and green chilies for 30 seconds. Stir in soy sauce, red chili sauce, vinegar, sugar, and sesame oil. Simmer for 2 minutes.
Add Vegetables: Toss in onions and bell peppers. Cook for 2 minutes, keeping them slightly crisp.
Combine Everything: Return the fried chicken to the pan. Stir well to coat with sauce. Cook for another 2 minutes.
Serve: Garnish with chopped spring onions and toasted sesame seeds. Serve hot with steamed rice or noodles.