Cream of Asparagus Soup

This soup is heavenly. I have also experimented with adapting it to be a pasta sauce, which worked well too.

1kg (2lb) asparagus spears
30g (1oz) butter
1 onion, finely chopped
4 cups chicken stock
1/4 cup basil leaves, chopped
1 teaspoon celery salt
1 cup cream

Break the woody ends off the asparagus, chop off the tips and blanch them in boiling water for 1-2 minutes. Chop the remaining asparagus into large pieces. Melt the onion and lighlty fry the onion. Add the chopped asparagus and cook 1-2 min. Add chicken stock, basil and celery salt and bring to the boil. Reduce heat and simmer gently, covered for 30 min. Check that the asparagus is very soft, then blend until smooth in a food processor or blender. Return to heat, add cream and season with salt and pepper. Do not allow to boil. Add blanched asparagus tips and serve immediately.
Serves 4-6