This pasty is made in 4 parts, meat, sauce, pastry and then putting them together. This allows for things to be made in batches independently from each other. It is done for efficiency, as the filling can be frozen ahead of time, and thawed prior to use. Pastry dough while able to be frozen, has a harder time recovering from the thawing process and is better when made a day or so prior to usage. Full recipe here.