Melt the butter, add the parsnips and apple, cover and simmer for about 10 minutes, stirring occasionally. Add the stock, sage leaves and cloves. Bring to a boil, cover and cook for about 30 minutes until the parsnips are tender. Remove the sage leaves and cloves and allow to cool a little, then puree. Add the cream and warm up slowly, but no longer boil. Serve sprinkled with sage and croutons.