Jerusalem Artichoke soup

from Susan (Stephanie Alexander’s recipe from The Cook’s Companion) Jerusalem Artichoke Soup 60 gm butter500 gm Jerusalem artichokes, scrubbed and cut into even chunks  1 onion, sliced1 clove garlic, lightly crushed1 stick celery, finely sliced1 potato or sweet potato, diced1 litre chicken stocksalt and pepperfreshly snipped chivesfreshly grated nutmegthick cream (optional) Melt butter in a heavy based [more]