Heat some of your fat in a heavy bottomed ovenproof pan and sauté the onions gently until just beginning to colour (Careful not to burn them) this should take about 6 - 7 minutes.

Remove them and set aside.

Now season the flour with salt, pepper and the mustard powder and coat the beef in the mixture. I usually do this is a zip-loc© bag (see my video) which saves a lot of mess.

Add more fat to your pan and fry the beef in several batches until nicely browned all over, then continue to do the same with the kidney.

Add all the beef, kidney and onions to your pot, add a little of the stock and scrape up all the brown bits on the pan bottom, this is where most of the flavour is so don’t waste it.

Bring to the boil, cover with a lid and into the oven at 170ºC for about 1hr 45 mins to 2 hrs or until the beef in nice and tender.

Remove from oven and leave until properly COLD, you cannot make pies with a warm filling, the pastry will go very soggy.

Divide your pastry and line the bottom of whatever pie dish you are using and fill with the cold filling. Make sure you fill to the top otherwise you pastry lid will sink down onto the filling and will not crisp up properly.

Wet the top edge of the pastry base then place on the top and make sure the two layers of pastry are well sealed.

Brush the top with a beaten egg and bake at 180ºC for about 45 - 60 minutes depending on the size of your pie. You will see when the to is crisp and nicely coloured.

Allow to rest for about 15 minutes before serving.