Add chicken pieces along with tomato sauce, sweet chilli sauce, soy sauce, garlic paste, ginger paste, ground pepper, and water into a deep pan. Place it on the stove, cover with a lid, and let it come to a boil. Then turn down the heat to medium, and simmer until chicken is half-cooked. Check the seasoning, and add more salt if needed. Now you can remove chicken from the gravy and leave it to cool.
Meanwhile mix cornflour (cornstarch) and water together, and add it to the chicken gravy. Simmer until it thickens. Your sauce is ready.
Now make a smooth batter using flour, egg, turmeric and water. Season with salt. Heat oil in a deep pan over high heat. (You can use a deep fryer instead). Dip the chicken pieces first in batter, and then roll in breadcrumbs. Deep fry until it turns golden brown and cooked through.
Alternatively, you can bake these in the oven at 200 C / 400 F for 15-20 minutes.
Serve chicken with sauce and French fries.