Fry the bacon over a medium heat in a large saucepan. Once the bacon is cooked, remove half and set aside. Continue to fry the remaining bacon until crisp. Remove from the saucepan and place in a separate bowl, then pour the bacon fat into another small bowl. Set aside. Heat the butter in the same saucepan and add the leeks and celery. Cook over a low to medium heat for about 10 minutes until the vegetables are soft and golden. Add the tomatoes, potato,
basil and bay leaves and stir well. Cover with a tight-fitting lid and simmer over a gentle heat for 30 minutes, without removing the lid.
Stir in the tomato paste and soft bacon, then remove from the heat. Blend in a food processor until smooth. Return to the saucepan and add the stock. Cook until steaming, then add the lemon juice and sugar, and season with salt and freshly ground pepper. Remove from the heat. Serve with a spoonful of cream, sprinkled with crisp bacon and croutons (method below).
Croutons: Heat the reserved bacon
fat in a large non-stick frying pan over
a medium heat. Cut the bread into cubes and fry until crisp and golden. (Add a little oil if necessary.)