Cut fillets into pieces that are about 5-6. 5 cm long and 4 cm wide.
Spread the pieces out in a single layer in a large plate and sprinkle with about 1/3 tsp of salt and 1 tbs of lemon juice.
Turn the pieces over and repeat with another 1/3 tsp of salt and 1 tbs of lemon juice. Set the plate at a tilt and leave it tilted for 2-3 hours.
As water accumulates at one end, discard it. Put the green coriander, green chillies, garlic, 1/4 tsp of salt and tbsp of water into the blender.
Blend until you have a paste. Empty the paste into a deep dish or shallow bowl. Put the yogurt into another deep dish or shallow bowl.
Add 1/4 tsp of salt to the yogurt and mix it in. Set the oil to heat in a wok, karhai or frying pan over a medium flame.
When very hot, dip 2 or 3 pieces of fish, first in the yogurt and then in the green paste to cover thoroughly and then put them in the hot oil.
Fry for about 5 minutes, turning the pieces over once, until the fish is cooked through. Remove with a slotted spoon.
Fry all the pieces of fish this way.
Serve the fried fish hot with green chutney.