Heat 1 tablespoon of the oil in a large pan and fry the bacon until it is crisp and golden. Remove with a slotted spoon and set aside to drain on kitchen paper.
Melt the butter and remaining oil in the pan over a medium heat and cook the onion, garlic, celery and leek, stirring frequently, for about 10 minutes or until soft and golden.
Add the stock and butter beans with the herbs and season to taste. Bring to the boil, then turn the heat down and simmer gently for about 10 minutes before removing from the heat. Remove the herbs and blend until smooth.
Stir in the cream, season to taste and serve in large bowls, scattered with crispy bacon.