Heat the oil and fry the fish pieces till crispy and brown. Remove and cool.
Remove the bones from the fish and place the fried fish flesh into a mixing bowl.
In the same pan, remove most of the oil leaving only 2 tbsp. Add the onion pieces and fry till light golden brown. Add salt to taste and also mix in the green chillies. Remove from fire and add to the fish pieces in the mixing bowl and toss gently.