Combine everything but the blue food colouring into a saucepan.
Cook for about 30 minutes until potatoes become mush.
Mash up potatoes and veggie mixture.
(If you are impatient, you can put this into a blender or food processor to puree- just like Bridget did. But be careful, WARNING: make sure the soup is not boiling hot when you pour it into the blender or food processor- or else the same thing will happen to you that happened to Bridget where the contents comes spewing out all over the room. And let me tell you, you will NOT be yelling "Oh Bugger! Oh Bugger Bugger!" you will be screaming bloody murder and in the hospital with 3rd degree burns. Make sure you cool the mixture first please - remember, Bridget Jones's Diary was a movie, in real life what she did was quite dangerous).
After the soup is pureed, add a couple of drops of blue food colouring- how much is up to you and how blue you want your soup to be.
Mix soup well to blend in the food colouring.
Just before serving, add a little sour cream on top of blue soup if you desire and garnish with chopped chives.
If you are seriously a die hard Bridget fan, you can add a few strands of string- but I don't recommend it- this is meant to be a delicious, edible version of this novelty soup.