Leek & Mushroom Pie re-edit

Pie!

Here's a nice pie:

This fed 6 people, with more to spare: It was a big pie.
200g cheese of your choice
1Kilo mushrooms, cleaned and quartered
1Kilo leeks, chopped,
2 big onions, chopped
1.5 tablespoon of flour,
glass of milk
an egg
salt and pepper

packets of frozen pastry (in my case accidentally puff pastry, but who knew?)
(enough pastry to line and roof a big oven dish, mine was about 45*25*10cm)

Sooo, in a pot, fry the onion, leek and mushrooms in a little oil, over a medium heat until they look cooked - the mushrooms will get a lot smaller, and add a bit of salt and pepper to taste at some point (I don't think it really matters when).

Low heat now. Then stir in the flour, and then the milk. Stir it quite vigorously. It should be a sticky mixture, not excessively liquid.
Line the dish with pastry, and cut a lid of pastry for the it.

Now, mix the cheese into the mixture... then fill the dish with it. Carefully put the lid on, pressing the edges with a fork so it's sealed. Make a couple of incisions in it, then brush it with some of the egg - which you will have beaten!

Use excess pastry to make decorative shapes, to stick on the lid of the pie (paint with egg too).

After that, stick the dish in a pre-heated oven at 180 degrees (centigrade!), for about 45 mins, 'till the pastry looks golden brown.

It's done. We had it with a salad.... It was a very good pie! Thanks for the help :)