2 lb (900 g) Jerusalem artichokes

2 slices of lemon

2 tbsp (1 oz) 25 g butter

4 oz (100 g) onion, skinned and chopped

2 level tbsp cornflour (cornstarch)

3/4 pint (400 ml) milk

25 ml (1 1/2 tbsps) lemon juice

2 tbsp (30 ml) chopped parsley

7.5 ml (1/2 level tsps) salt

pepper

113 ml (4 fl oz) carton single cream

1. Wash the artichokes well and put them in a large saucepan with the lemon slices. Cover with water, bring to the boil and cook until tender, about 20 minutes. Drain of the water and reserve 600 ml (1 pt). Allow the artichokes to cool before peeling away the skins. Roughly mash them.

2. Melt the butter in a clean saucepan, add the onion and fry until soft but not coloured. Stir in the cornflour, reserved artichoke water and milk. Stir in the artichokes.

3. Bring the sauce to the boil, stirring. Cook for 2-3 minutes, then sieve the soup or puree in an electric blender.

4. Return the soup to the saucepan. Stir in the lemon juice, parsley, seasoning and cream.

5. Bring to serving temperature. Garnish with croutons.