Oude Rotterdamse kaas or old Rotterdam cheese is a recent favourite of mine. It has a lovely nutty flavour and I thought it would work well with this pie. The oude or old refers to the fact it has been matured longer for extra flavour. For those of you without access to this Dutch cheese, Keens cheddar is always a nice substitute. 
Wild garlic is just starting to come into season and has a lovely kick to it, reminiscent of a cross between garlic and chives and works well with the cheese and leeks in this dish.

This makes enough for 1 pie in an 8 inch pastry ring
To make the pastry
170g plain white flour
85g butter
45ml iced water
pinch salt
Beaten egg yolk to glaze the pastry

Rub the butter and flour together until it resembles bread crumbs 
Add the egg yolk and water and bring the mixture together until it forms a stiff dough
(this can also be made in a food processor, simply whizz the flour and butter mix until it resembles bread crumbs, then add the egg yolk and then some of the water until it comes together)
Wrap the pastry in cling film and place in the fridge for an hour to rest
Once the pastry has rested, roll out to 5mm thick 

See steps in pictures below


Then take the cut out pastry and press into the edges of the pastry ring, make sure there are no air bubbles 



Trim any excess pastry from the edges of the ring using a knife 
Roll out the rest of the pastry until it is slightly bigger than the pastry ring about 5mm thick, this will be your lid
Place the lined pastry ring and rolled out pastry in the fridge for 30 mins

Pie filling
250g cheese grated
70g leek finely chopped
70g wild garlic finely chopped
50g creme fraiche
15g dutch mustard (or Dijon)
30g butter
salt and pepper to taste

Fry the leeks off in the butter on a low heat until soft and glossy and place to one side to cool
In a bowl, add the cooked leeks, cheese, creme fraiche, mustard and garlic and mix together
Season to taste with the salt and pepper
Fill the bottom of the pastry ring with the pie mix

Brush the sides with the egg wash and place the lid on top of the pie, trim off the excess pastry

Press the sides of the top to ensure it is all sealed, see pictures below



With a knife make a small slit in the top to allow steam to escape

To finish glaze with the beaten egg
Bake at 190c (fan), 200c (normal) for 30 mins and the pastry is golden brown in colour