Photo: Helen Peacocke 15/10/2008Adding an apple to root vegetables such as parsnip heightens the flavour of the parsnip.This recipe is a great way of using up the glut of apples many gardeners are facing this year.To serve 4 people you will need:4 medium parsnips1 large cooking apple2 medium potatoes1 large onion2 tspns chopped fresh sage leaves1 tspn chopped parsley1 oz (25g) butter1 pt (600ml) v