Heat mustard oil in a pan and sauté chopped onions until soft.
Add green chilies and turmeric powder, cook for 1 minute.
Add flaked fish and mix well with spices.
Add salt and cook until the mixture becomes dry.
Turn off the heat and mix fresh coriander leaves.
Let the filling cool completely.
Fill the mixture into samosa sheets and fold into triangle shapes.
Deep fry in hot oil until crispy and golden brown.