Heat oil in a kadai.Take all the batter ingredients and add water to it. Form this into a smooth paste. Dip the fish pieces in it and fry them in hot oil for 5 mins till they are golden and cooked through. Drain them in a paper towel.
Now make the sauce. Heat oil in a kadai.
Add in ginger garlic paste and mix well.
Add in onions, green chillies and mix well. Cook this for a min.
Add in tomatoes and toss well in the oil. Let them cook for a min.
Add some salt and sugar to it and mix well.
Now add in red chilli paste, soy sauce, green chilli sauce, ketchup, vinegar and mix well.
Add some water to it and mix well to form a sauce. Let them come to a boil.
Add in the corn flour slurry (corn flour mixed with water). Actually I added some of the left over batter. Mix well so that it gets thick and saucy.
Add in pepper and mix well.
Add the fried fish pieces in this and toss well with the sauce.
Garnish with coriander leaves or spring onions and mix well.