Watercress soup

Oh dear, you know when you do something and then make a rod for your own back. Homemade soup yesterday went down so well, that I got another request today. It's just as well that soup is so easy to make, chuck it in, simmer, whizz it with a hand blender and you have soup.

Watercress soup
2 tblsp olive oil
1 large onion
2 large potatoes
1 pint chicken stock
1 bag of watercress, washed
double cream
salt & pepper

Chop the onion, saute in a pan until soft. Add the chopped potato, cover with chicken stock, add the watercress, bring to boil and then simmer until the vegetables are soft. Whizz soup with hand blender until smooth, season to taste and thin with water if required. Add a couple of tablespoons of double cream and stir. Serve and add a swirl of double cream if desired.