When I'm making a pie for a dinner plate size I use 4oz of plain flour, 1.5 tsps baking powder, 1 oz of butter and 1oz of white Flora. (If you don't have white flora you can use an egg). Rub together for about a minute until you get fine crumbs, add cold water slowly until you form a dough. Put in the fridge while you prepare the apples. Roll out, add apples and sugar to taste - I usually use 3 dessert spoons. Brush the top with milk. Cook at gas mark 5 for 30-40 minutes. The basic rule is half fat to flour. Try to keep everything as cold as possible - I run the tap over my wrists before I start rubbing the fat into the flour.