2 lb (900 g) Jerusalem artichokes
2 slices of lemon
2 tbsp (25 g) 1 oz butter
1 medium onion, skinned and chopped
450 ml (3/4 pint) milk
15 - 30 ml (1-2 tbsp) lemon juice
15 - 30 ml (1-2 tbsp) chopped fresh parsley
5 -10 ml (1 - 2 level tsp) salt
freshly ground pepper
4 tbsp (60 ml) fresh single cream
1. Wash and peel the artichokes. Place in a large saucepan with 900 ml (1 1/2 pints) cold salted water and lemon slices. Bring to the boil and simmer gently for 25 minutes until tender.
2. Drain, reserving the cooking liquid, and make up to 600 ml (1 pint) with water. Mash the artichokes. Discard the lemon slices.
3. Melt the butter in a clean pan, add the onion and cook for about 5 minutes until soft but not coloured. Remove the pan from the heat, stir in the cornflour and gradually add the reserved artichoke cooking liquid and milk.
4. Add the artichokes and bring to the boil, stirring. Cook for 2-3 minutes.
5. Cool the soup. Puree in a blender or rub through a sieve and return to the saucepan. Stir in the lemon juice, parsley, seasoning and fresh cream.
6. Reheat gently but do not boil. Garnish with croutons.