1.Preheat the oven to 185°C. Line a rectangular tin with the pastry sheets, trimming to fit neatly. Chill until required.
2.Heat the butter in a medium frying pan and sauté the leek for 4-5 minutes over a gentle heat until soft but not coloured.
3.Transfer to a bowl and cool for 5 minutes before adding the salmon, capers, dill, eggs, cream and seasoning. Sprinkle the grated cheese over the pastry base, then spoon in the salmon cream filling, arranging evenly.
4.Bake for 30-40 minutes until the pastry is golden and the filling is set. Serve with crème fraîche, mesclun and extra dill and capers, if desired.