Remove scales and ridges by scraping from tail to head on both sides of the fish.

Cut off the head by slicing diagonally behind the pectoral and ventral fins, hitting the backbone.

Remove the internal organs and rinse the fish under running water. Pat dry with kitchen paper.

Butterfly the fish by slicing along the backbone from the tail to the head, lifting the flesh gently as you cut.

Remove the backbone by slicing along it and pulling it away from the flesh, cutting near the tail to detach.