Cut the fish into finger pieces.
Make a batter with corn flour, maida, baking powder, soy sauce, celery, pepper powder, water and salt.
Dip the fish pieces in the batter and fry in oil till golden brown. Transfer fish into a serving plate.
For the sauce:
Heat oil in a pan.
Saute garlic, ginger and green chilly. Add soy sauce, chilly and tomato sauce to it.
Finally add corn flour mixed with water to it and stir well. Once it starts to boil, remove form fire.
At the time of serving, pour the sauce on top of fried fish pieces and mix well.
Garnish with chopped spring onions.