To make the stock, heat a large pan with a dash of oil and brown the bacon bones. Add the onion, celery and carrot and sauté for 3-4 minutes before adding 4 cups of water and the bay leaf. Bring to the boil and simmer for 30-40 minutes. Strain the stock, reserving the liquid for the soup. Remove the meat left on the bacon bones to add to the soup. Discard vegetables and bay leaf.