Cut the steak in small bits, fry in a pan with the margerine, until cooked through
Add the flour and fry for a bit.
slowly add the stock and cook until thickened
Allow the beef to cool
Add some of the steak to the middle of the sheet of puff pastry
Mix egg, and brush some egg long the sides of the bottom sheet of pastry.
Place a new one on top and use a fork to press down on the sides. Over the top of the pastry with egg.
Bake in an oven at 220 for 12-20 mins until golden brown.
These are details from the first attempt to cook a steak bake, similar to gregs. I used an oxo stock cube, but would try another next time.
The 75g sheets of puff pastry are too thick, roll out to half size next time. Should be enough for 1 pastry.