Steak and banger Pie

This pie is made using cubed up steak, English banger's (Specialty stores carry these) mushrooms, leeks and homemade beef stock simmered till the steak is very tender.  To make the beef stock I use ox tails rolled in flour and simmer for hours upon hours with salt, pepper, pepper flakes and water.
I used hot water pastry for the crust.  I let the filling cool and sort of jell so it's not too runny before I put the filling into the pie.