Place the cubes of beef into a large bowl and pour over the red wine and 2 tbsp of Worcestershire sauce.
Add a few sprigs of thyme, cover and leave to marinate for a few hours.
Preheat the oven to 150ºC.
Peel and dice the onion and carrot.
Dice the mushroom into large cubes.
Drain the beef, but save the marinade for later.
Toss the beef in 2 tbsp of plain flour.
Heat the oil in a large ovenproof saucepan and add the beef.
Fry to colour well, then add the onion, carrot and mushrooms, continuing to cook for a few more minutes.
Squeeze in the tomato purée and coat everything in it.
Pour the beef marinade into the saucepan, let it bubble for a few minutes then add in the beef stock.
Put a lid on the pan and place it in the oven.
Cook for 2 hours, then strain through a sieve to separate half the liquid and set aside to cool.
Rub the butter into the flour to form a breadcrumb consistency.
Pour the remaining 4 tbsp of Worcestershire Sauce and enough cold water into the mixture to form a dough.
Squeeze the dough together into a ball of pastry and rest in the fridge for an hour.
Raise the temperature of the oven to 180ºC.
Roll the pastry out on a floured surface to approximately 1cm thick.
Spoon the steak and mushroom pie filling into 4 individual pie dishes and cut the pastry out to fit on top.
Brush around the edges of the pie dish with egg wash.
Lay the pastry over the pie and crimp the edges together to seal it in.
Brush the whole top of the pies with egg wash, then place them onto a baking tray.
Bake in the oven for 20 minutes, until evenly golden brown.
Fry the sliced red onion in a frying pan with a knob of butter until soft and sweet, then add the strain liquid from the pie filling that you saved.
Heat to a bubble, season with salt and pepper and stir in enough hot water to give you your preferred gravy consistency.
Serve the baked pie with steamed green veg and boat of gravy!