1 small head of celery, stalk removed and leaves reserved
1 medium leek, roughly chopped and washed
1tbsp vegetable or corn oil
½tbsp plain flour
2ltrs vegetable stock
Salt and freshly ground black pepper
150g soft blue cheese mixed with a couple of tablespoons of single cream
Reserve about 2 or 3 of the centre stems of celery and cut them into ½cm dice. Blanch for 2-3 minutes in lightly salted water until tender, then drain.
Meanwhile, roughly chop the rest of the celery, also reserving the leaves. Heat the vegetable oil in a heavy saucepan; gently cook the leeks and celery for 3-4 minutes with a lid on until they soften.
Stir in the flour, then gradually add the vegetable stock and bring to the boil. Season and simmer gently for 30 minutes, add the leaves, remove from the heat and blend in a liquidiser until smooth.
Strain through a sieve and leave to cool, then chill in the refrigerator.
To serve, re-season to taste and stir in the diced celery. Pour into soup bowls and spoon blobs of the blue cheese into the soup.