For the pastry, combine the flour, salt and lard and rub together until the mixture resembles breadcrumbs - this can be done in an industrial food processor or in batches.
Either by hand, or with the motor still running, gradually add the water in a thin stream until the mixture comes together as a dough.
Wrap the pastry in cling film and chill in the fridge for 30 minutes.
Preheat the oven to 180C/350F/Gas 4.
For the filling, place the chopped beef and flour in a large bowl and mix until the meat is coated in the flour. Season, to taste, with salt and freshly ground black pepper.
When the pastry has chilled, divide it into 40 even sized pieces. Roll out each piece of pastry onto a lightly floured work surface until it is just larger than a dinner plate. Make sure not to tear the pastry.
Using a dinner plate as a template, trim the edges of each piece of pastry to form a disc.
Spoon some of the chopped potato onto one half of each pastry disc, leaving 1.5cm/Â¾in free along the edges.
Spoon some of the chopped swede on top of the layer of potato, and then spoon some of the chopped onion on top of the layer of swede. Finally, spoon over some of the beef.
Brush all round the edges of the pastry lightly with a little of the beaten egg.
Fold the empty half of the pastry disc over the filled half and either press the edges together with a fork, or twist the edges to seal.
Brush the top of each pasty with more beaten egg. Using a sharp knife, cut a small cross shape in the top of the pasties through which the steam can escape. Repeat the process with the remaining pastry, vegetables and meat.
Place the pasties onto a baking tray and transfer to the oven. Bake for 45-50 minutes, or until the pastry is crisp and golden-brown and the filling is cooked through and piping hot.
When the pasties are cooked, remove them from the oven and set aside to rest for 5-10 minutes before serving.