Cut one leek into 4 slices, lengthways and reserve. Chop the remaining leeks.
Heat margarine and sauté the chopped leeks, celery and carrot until soft. Stir in the flour and cook for 1 minute, stirring.
Add the stockpot, boiling water and cream. Cook stirring until the mixture thickens. Toss the fish in fish spice and then add the fish to the pan and simmer gently until fish is cooked through. Stir in the parsley and turmeric.
Preheat the oven to 200°C.
Spoon the mixture into 4 x 1 cup capacity ovenproof dishes.
Brush the edges with egg, top with pastry, trim. Brush pastry with egg. Push a slice of reserved leek on top.
Bake in preheated oven for 20 minutes on until pastry has puffed up and is golden.