Coarsely chop the prawns, keep aside.
Heat 1 tbsp oil in a pan, add the chopped onions, ginger and garlic, fry till a gorgeous golden.
Add the chopped green chillies, saute for a minute or two.
Add the fish, prawns, red chili powder, tomato ketchup, salt and sugar.
Cook over a low flame, stirring occasionally, 10-12 minutes I would reckon, till the fish and prawns are cooked and almost all the water released has dried off.
Adjust seasonings. Finish off with coriander leaves and just a hint of garam masala powder.
Allow to cool to room temperature.