To begin, cut the boneless chicken breasts into bite-sized pieces.
Marinate with ginger garlic paste, light soy sauce, baking soda, salt, and an egg. Mix well and keep aside to marinate for at least 30 minutes. The longer the better.
For the second marinade, add cornflour and oil. Mix well and keep aside for a few minutes.
In the meantime, prepare the sauce mixture. In a bowl, mix together light soy, oyster sauce, tomato ketchup, chilli sauce, and vinegar. Mix well and keep aside.
Heat oil for deep frying. Add in the chicken pieces in batches on high heat. Then reduce the heat and fry until cooked. Make sure they do not brown.
Heat 2 tbsp of sesame oil in a pan. Add in finely chopped garlic and ginger. Saute for a minute. Add in the chopped green chillies and saute some more.
Next, add in diced onions, diced bell peppers, and black pepper powder. Cook for a minute or two.
Add in the sauce mixture and cook some more.
Add in a slurry of 1 tbsp cornflour mixed in 1 tbsp of water. Cook until the sauce thickens.
Finally, add in the fried chicken pieces and mix until well coated.
Add in a bit of water and adjust the gravy as per your taste.
The Chicken Manchurian is ready to serve. Garnish with spring onion greens and serve hot with noodles or rice.