For the pastry, place the lard, milk and water into a small pan and gently heat until the lard has melted.
Sift the flour into a large bowl and season with salt and freshly ground black pepper and mix well.
Make a well in the flour and pour in the warm lard mixture. Mix well to combine, until the mixture comes together to form a dough. Knead for a few minutes, then form into a ball and set aside.
For the pork jelly, place all of the pork jelly ingredients into a large pan and pour in enough water to just cover. Bring slowly to the boil, then reduce the heat to a simmer. Cook for three hours over a low heat, skimming off any scum that rises to the surface, then strain the stock through a fine sieve and discard the solids.
Pour the sieved stock into a clean pan and simmer over a medium heat until the liquid has reduced to approximately 500ml/1 pint.
For the pie filling, place all of the pie filling ingredients into a large bowl and mix well with your hands. Season with salt and freshly ground black pepper.
Preheat the oven to 180C/350F/Gas 4.
Line a pork pie dolly (or a jam jar) with cling film to prevent the pastry from sticking.
Pinch off a quarter of the pastry and set aside. On a floured work surface, roll out the remaining three-quarters of pastry into a round disc about 3cm/1¼in thick. Place the pie dolly into the middle of the pastry circle and draw the edges of the pastry up around the sides of the dolly to create the pie casing. Carefully remove the dolly from the pastry once your pie casing is formed.
Roll the pork pie filling into a ball and carefully place into the bottom of the pastry case.
Roll out the remaining piece of pastry into a circle large enough to cover the pastry case as a lid.
Brush the top inner parts of the pastry casing with some of the beaten egg and place the pastry circle on top. Pinch the edges of the pastry to seal the pie. Brush the top of the pie with the rest of the beaten egg, then bake in the oven for 45 minutes to one hour, or until the pie is golden-brown all over.
Remove the pie from the oven and set aside to cool. Cut two small holes in the top of the pork pie and pour in the pork jelly mixture (you may need to heat it through gently to loosen the mixture for pouring). Chill in the fridge until the jelly is set.
To serve, cut the pie into slices and serve with piccalilli or chutney.