The meat filling for this can be prepared ahead of time, and when the meat has cooled, kept in the fridge - indeed, the flavour will improve. The pastry covering is better completed just before cooking.
For a 1.8 litre deep pie bowl - enough to serve 6 people:
1 big Onion, peeled and sliced
1 clove of Garlic, peeled and chopped
1kg Beef, Chuck Steak or Skirt - trimmed of fat and cut into cubes
250g lamb or veal kidney, trimmed of any centre sinew, and cubed
250g cap or flat mushrooms, wiped an cut into wedges
400ml beef stock, Beer or Guinness
Salt and freshly-ground black Pepper
1 tablespoon (15ml) Tomato Purée
250gr packet of puff pastry
1 egg - lightly beaten
1. Melt half the butter in a big, heavy frying pan, and lightly brown the onions, add the chopped garlic for the last minute of cooking.
2. Remove them from the pan, and set aside.
3. Brown the steak and kidney over a medium heat, in the remaining butter - in batches if necessary. Keep the kidneys separate, and set them aside.
4. Remove from the pan, and set aside.
5. Deglaze the frying pan with a little of your chosen liquid, scrapping the base to remove any dark caramel - add this liquid to the meat.
You can keep this meat filling in the fridge until it's needed.
6. Roll the puff pastry out until on a very lightly-floured surface, until you have a shape quite a bit larger than your chosen pie dish. Remove pastry strips from all the edges, and return all to the fridge, while you cook the meat.
7. Mix the meat, onions and your chosen liquid together and put them into a casserole or large lidded saucepan and season lightly with salt and pepper.
8. Cook the meat, as slowly as possible - either on top of the stove, or in the oven at 150°C, for 1½ hours (or 3 hours in a slow cooker). Remove from the oven, and add the 'sealed' kidneys, the tomato purée and sliced mushrooms - gently mix these ingredients in.
9. Cover again, and return to the oven for a further 30 minutes.
10. Remove from the oven.
At this point you have two choices -
1.To allow the mixture to completely cool, then refrigerate until needed.
2.Finish baking the pie at this point.
11. If finishing now, transfer the meat mixture to an ovenproof pie dish, dampen the rim of the dish with a little water and press the saved pastry strips on to the rims. Heat the oven to 450°F/230°C/ Gas 8.
12. Now moisten the top edges of the pastry strips with water before carefully placing the main piece of pastry on top. With a pastry brush, coat the pastry with a little of the beaten egg.
13. Make a few small air-holes in the top of the pastry to allow steam to escape.
14. Put the pie on a baking tray, in case there are any leakages, and place in the oven.
15. After 10 minutes, reduce the heat to 350°F/180°C/ Gas 4, and bake for a further 20 minutes, or until the pastry is golden.