Cut steak into 1/2 inch cubes.
Peel potatoes, slice thin, then dice.
Mix meat, potatoes and onion.
Season with salt and lots of pepper.
Divide pastry into 4 parts.
Roll each into a 9 inch circle.
Heap 1/4 of the filling on half the circle.
Sprinkle with parsley and dot with butter.
Carefully fold pastry over filling, crimp edges together to seal.
Prick top with fork.
Bake in oven at 400° about 15 minutes.
Reduce heat to 350°.
Bake for 45 minutes to 1 hour