1.Heat 2 teaspoons of the oil in a 6-litre (24-cup) pressure cooker, cook mushrooms until browned. Remove from cooker.
2.Heat 2 teaspoons of the oil in cooker, cook kidney until browned. Remove from cooker.
3.Season flour in a large bowl, add beef, toss to coat in flour. Shake off excess. Heat half the remaining oil in cooker, cook beef, in batches, until browned. Remove from cooker.
4.Heat remaining oil in cooker, cook onion, carrot and celery, stirring, until tender. Return beef to cooker with thyme, bay leaf and the water, secure lid. Bring cooker to high pressure. Reduce heat to stabilise pressure cook 25 minutes.
5.Meanwhile, preheat oven to 210°C (200°C fan forced).
6.Release pressure using the quick release method, remove lid, discard thyme and bay leaf. Stir in mushrooms and kidney, season to taste. Spoon hot steak and kidney mixture into 1.5-litre (6-cup) deep ovenproof pie dish. Place pastry over filling, trim edge, cut two small slits in centre of pastry. Brush pastry with egg. Bake for 25 minutes or until well browned.
If you have an electric pressure cooker you won’t need to reduce the heat to stabilise pressure, your cooker will automatically stabilise itself. Always check with the manufacturer’s instructions before using. The steak and kidney filling is suitable to freeze.