Green Garden Soup

4 celery stalks, chopped
2 leeks, washed and shredded
1 bunch watercress stalks, trimmed
3 courgettes, thinly sliced
600 ml/1 pint chicken stock
salt
freshly ground black pepper
1 clove garlic, peeled and crushed
small bunch of parsley
150 ml 1/4 pint plain low-fat yogurt
snipped chives, to garnish

Put the celery, leeks, watercress and courgettes into a saucepan together with the chicken stock, salt and pepper to taste, garlic and parsley. Simmer gently until the vegetables are just tender - about 15 minutes.

Puree in a blender or food processor until smooth. Cool, then stir in half the yogurt. Chill in the refrigerator.