Parboil the leeks in salted water for 5 minutes. Drain very well. Fill a 1.1 litre (2 pint) pie dish with the leeks and pork. Season to taste and pour in the milk.
Cover with foil and bake at 200˚C (400˚F) mark 6 for about an hour. (Don’t worry if it looks curdled).
Stir the cream into the eggs, and then pour into the dish. Allow to cool.
Roll out the pastry on a floured surface to 5cm (2 inches) wider than the dish. Cut a 2.5cm (1 inch) strip from the outer edge and use to line the dampened rim of the pie dish. Dampen the pastry rim with water, cover with the pastry lid and seal the edges well, then knock up and flute. Make a hole in the centre of the pie and use pastry trimmings to decorate.