The green or brown lentils in this classic rustic Italian soup take on the flavour of the bay leaves and rosemary, and give the soup a wonderful texture.
Place the lentils in a bowl and cover with cold water. Leave to soak for 2 hours. Rinse and drain well.
Heat the oil in a pan. Add the bacon and cook for 3 minutes, then stir in the onion and cook gently for 5 minutes, or until softened. Stir in the celery, carrots, rosemary, bay leaves and lentils and toss over the heat for 1 minute.