Preheat the oven to 160C/320F/gas 2.5.
Grease the pie dish with butter.
Heat a little lard in the frying pan until melted and hot. Fry the beef in batches until browned. This needs to be done in batches to avoid overcrowding the frying pan. Transfer each batch to the shallow dish and set aside.
Heat a little lard in the casserole and add the lardons. Cook until browned.
Add the browned beef, season well and cover with the water.
Bring to the boil. Immediately remove from the heat, cover and place in the preheated oven for 2 hours or until the beef is tender.
Remove from the oven and allow to cool thoroughly.
Heat the butter in the frying pan, add the leeks and sauté on a moderate heat until soft. Remove from the heat and set aside.
When the meat is cooled remove any fat which has risen to the surface, strain the meat from the gravy and put into the bowl.
Return the liquid to the casserole and bring to the boil, adding the cornflour mixture. Simmer until the gravy has reduced and thickened.
Raise the temperature of the oven to 180C/350F/gas 4.
To make the pastry sift the flour and salt into the mixing bowl or food processor bowl.
Add the butter and lard and rub in (or process if using a food processor) until the mixture resembles fine breadcrumbs.
Place the egg yolk in the cup and add the ice cold water and whisk together.
Add to the pastry mix and bring together to make a dough adding more water if the dough is too dry. If using a processor add the egg mixture and whizz until the mixture forms a ball of dough.
Wrap in clingfilm and chill in the fridge for 30 minutes.
Fill the pie dish with alternate layers of meat and leeks, topping with a layer of leeks. Pour over the rich gravy.
Remove the pastry from the fridge and roll out to 1-2cm larger in diameter than the top of the pie dish.
Brush the rim of the pie dish with beaten egg.
Place the rolled-out pastry on top of the pie, crimping the sides to seal the edges.
Use any pastry trimmings to make decorations which you can stick onto the pie top with beaten egg. Brush over with the beaten egg.
Place in the oven for 30 minutes or until the pastry is cooked and golden and the filling is bubbling.
Remove from the oven and serve immediately.
