Slice 800 g (1¾ lb) Jerusalem artichokes and stew with 75 g (2½ oz) butter. Add 25 g (1 oz) crushed, roasted hazelnuts and 1 litre (1¾ pt or 4½ U.S. cups) White Bouillon; simmer gently until cooked. Pass through a fine sieve and adjust the consistency by thickening it with 40 g (1⅓ oz) arrowroot mixed with 2½ dl (9 fl oz or 1⅛ U.S. cups) cold milk. Bring to the boil then pass through a fine strainer; reheat and finish at the last moment with 150 g (5 oz) butter.
This soup may also be prepared as a Cream or a Veloute.