1 small lettuce (150g/5 ½ oz)
1.2 litres/2 pints vegetable stock
150ml/5fl oz single cream
Trim the lettuce and leek, and chop them into bite-sized pieces. Put them into a large saucepan with the vegetable stock. Bring to the boil, then simmer for 15 minutes until the vegetables are soft.
Remove from the heat and allow to cool a little, then transfer to the bowl of a food processor or liquidiser and process until very smooth.
Pour the soup back into the saucepan and stir in the cream. Reheat gently to serve.