On a floured work surface, roll out the dough into a disc (its diameter must be 2.5 cm / 1 inch larger than the dish). With a small 2.5 cm (1-inch) cookie cutter, make a hole in the centre of the dough to allow steam to escape from the pot pie. Place the dough over filling, folding in the edge of the dough. Cut off any excess. Cover with plastic wrap. Freeze at this stage or it is ready for baking.