In a medium sized saucepan, add the diced steak, chopped onions and bacon. Cover with water and add a stock cube (if using) and a splash of red wine (if using).
Bring to a boil then reduce to simmer, slightly covered, for 2 hours.
Season with salt and pepper.
Strain the liquid into a jug and place the meat filling into a bowl.
To make a thick gravy to go into the pie, melt about 30g of butter in a small saucepan and add about 2 tablespoons of plain flour to make a roux.
Cook for a couple of minutes, then add about 1 cup of the meat liquid and mix to make a thick, smooth gravy. Pour it over the meat filling and allow to cool.
Fill the pie with the meat filling
brush the edge with an egg wash and top with a sheet of puff pastry.
Press to seal and trim the edges
Place a couple of slits in the top and brush with egg wash. Bake at about 220°C for 30 minutes or until golden brown. Cool for 10 minutes before serving.