Make the pastry: rub the Strong Bread Flour with the Lard and Unsalted Butter until the mixture resembles coarse breadcrumbs. Stir in a pinch of Salt and add enough cold Water a little at a time to bring the dough together. Form into a disk, wrap and chill in the fridge for at least 30 minutes.
Prepare the filling vegetables first: peel and dice the Waxy Potatoes and the Swede into small, even cubes; finely chop the Onion.
Cut the Beef Skirt Steak into small dice (roughly the same size as the vegetables) so everything cooks evenly. Season the meat and veg with Salt and freshly ground Black Pepper, then toss together in a bowl.
Preheat the oven to 200°C (400°F). Lightly flour your work surface and divide the chilled pastry into four large portions. Roll each portion into a roughly 20cm (8in) circle.
Assemble the pasties: place a generous portion of the filling mixture onto one half of each pastry circle, leaving a clear border around the edge. Dot a little of the remaining unsalted butter over the filling if you like for extra richness.
Brush the pastry edge with a little beaten egg or water, fold the pastry over the filling to form a semicircle, and press the edges together. Crimp the edges by hand to seal the pasty securely.
Make the glaze by beating the Egg with the Milk and brush it over the tops of the pasties to give them a golden finish.
Bake on a lined tray for 40–50 minutes, or until the pastry is deep golden and the filling is cooked through. Allow the pasties to rest for 5–10 minutes before serving so the juices settle.
