Melt the butter in a saucepan and sauté the bacon and vegetables for 2 or 3 minutes.
Add the stock and bring to the boil
Reduce heat, cover and simmer for 45 minutes or until the vegetables are soft
Put the mixture in a food processor or blender until smooth.
Season with salt and pepper.
Chill for 2 hours
If you like, when it's cool, you can stir in cream.
Re-heat of course before serving.
Garnish with fresh coriander if you like