Place fries on an oiled baking tray/s and bake for 25 to 30 minutes or until golden and crisp (or check manufactures instructions).
Meanwhile fill a medium frying pan with water to 5cm deep and add 2 tablespoons of the lemon juice and bring to the boil over moderate heat and add fish, cover and reduce heat to low and poach fish for 5 minutes or until just cooked.
Using a slotted spoon transfer fish to a plate.
Melt butter in a medium saucepan over moderate heat and add leek and cook and stir for 4 to 5 minutes or until soft and the add flour and cook and stir for 1 minute.
Gradually add milk, stirring until mixture boils and thickens and then stir in the fish and vegie mix and simmer for 2 minutes or until heated through and then stir in chives and remaining juice.
Spoon hot mornay mix into 4 x 1 1/2 cup serving dishes and stand chips in mornay mix and then serve.