To make the pastry, sift the flour and a pinch of salt into a large bowl. Rub in the butter (or butter and shortening) with your fingertips until the mixture resembles fine breadcrumbs. Sprinkle 90 ml of chilled water evenly over the surface, then mix in with a round-bladed knife. If the dough seems dry, add a little extra water. Gather the dough together, then lightly knead on a floured work surface for a few seconds until smooth. Wrap in plastic wrap and chill in the refrigerator for 20 minutes before using.
Meanwhile, to make the filling, put the steak, onion, potato, pumpkin or swede, stock and parsley in a bowl. Season generously with salt and freshly ground black pepper and mix together well.
Preheat the oven to 200°C. Divide the pastry into eight pieces, then roll out each piece on a lightly floured work surface to a 20 cm round.
Spoon an equal amount of the filling onto the centre of each pastry round. Brush the pastry edges with beaten egg or milk, then bring together at the top. Press the edges firmly together to seal, then crimp the edges or make a pattern with a fork.
Place the pasties on two non-stick baking trays. (If you don't have non-stick baking trays, lightly grease two trays before using). Brush the pasties with beaten egg or milk. Make a small hole in the top of each one to allow some of the steam to escape.
Bake the pasties for 15 minutes, then reduce the oven temperature to 160°C and cook for a further 45 minutes to 1 hour, or until the pastry is nicely golden and the filling is cooked. (Test by piercing in several places with a fine skewer – it should go through with little resistance.) Serve hot, warm or cold.