To make the pie filling, put the steak and flour in a bowl and toss to coat.
Over a high heat, melt half the lard in a flameproof casserole. Once hot, add the beef and brown all over. You may need to do this in batches, to avoid overcrowding the dish and steaming the beef.
Add the onions, celery, carrots and tomato purée. Fry gently for 5–6 minutes until the vegetables are soft and golden-brown.
Add the stout, stock, mushrooms, soy sauce, sugar, bay leaves and thyme. Season generously with salt and pepper. Bring to the boil, then turn the heat down until just simmering. Cover with a lid and cook on the hob for 1½–2 hours, until the beef is tender. Once cooked,set aside to cool.
Meanwhile, make the pastry. Sift the flour and salt into a food processor or a mixing bowl. Add the chilled butter and lard and pulse or work together with your fingers until the mixture resembles coarse breadcrumbs. Add enough water to bring it together into a dough, then turn out onto a lightly floured work surface. Shape into a disc about 4–5cm/1.5–2in thick, then cover and chill until ready to use.
Preheat the oven to 190C/170C Fan/Gas 5.
Spoon the cooled filling into a 28x23cm/11x9in pie dish.
Roll the out pastry on a floured work surface until large enough to cover the top of your pie dish. Brush the edges of the pie dish with beaten egg to help the pastry stick, then lay the pastry over the filling. Make a little cut in the centre to release the steam, then brush with egg wash.
Bake for 30–35 minutes, or until the pastry is golden-brown and the filling bubbling hot. Serve in slices.
