1.Preheat oven to 180°C. Cook potatoes in a saucepan of boiling, salted water 15-20 minutes, until tender.
2.Meanwhile, melt butter in a medium saucepan on high. Saute leek 3-4 minutes, until tender. Add flour and cook, stirring, 1 minute. Remove from beat. Gradually add milk, stirring until smooth. Return pan to medium heat and cook, stirring constantly, until sauce boils and thickens. Reduce heat to low and simmer 3 minutes. Season to taste. Allow to cool slightly. Add salmon, spinach and dill.
3.Drain potatoes and mash well. Stir in extra butter and egg. Season to taste.
4.Spoon salmon mixture into a shallow 8- cup baking dish. Top evenly with mash, roughing up the surface with the back of a spoon. Sprinkle with combined parmesan and breadcrumbs.
5.Bake 25-30 minutes, until hot and the top is golden. Serve with steamed green beans and lemon wedges.