De-rind bacon, chop and mix with diced onions and apple, season with salt, pepper and fresh sage.
Divide filling between 4 individual pie dishes or into one large dish. Pour in the cider.
Roll out pastry to fit large enough to cut out four pie tops and place over dishes, pressing the edges well to seal.
Cut a cross in the centre of each pie and fold back the triangles to expose the filling. Brush tops with beaten egg and bake for 25 minutes until pastry is golden brown and filling bubbling, serve hot.