Cut the fish into thin slices and remove fish smell.
Grind onions, ginger, chillies, sugar and mustard seeds to a fine and smooth paste and mix into the curds along with the rest of the above ingredients.
Set aside for 1 hour, and then heat 4 tbsps. Mustard oil on a flat girdle or tawa to smoking, reduce heat and put in 2 curd-covered slices of fish.
Cover the slices and cook over a slow fire till they turn dry, then uncover and fry till brown and crisp.
Serve piping hot decorated with sprigs of coriander leaves.
Ingredients: 1 kg - hilsa
2 - big onions
1 big piece - ginger
4 - green chillies
1/4 tsp - sugar
200 g - sour curds
1 tbsps - turmeric powder
100 g - mustard seeds
salt and chilli powder to taste