Salt Freshly ground black pepper *Note: Finely chopped parsley may be substituted for coriander leaves. Wash lentils in several changes of cold water, or place in a sieve and run water through them. Drain. Put lentils in a large pot with 8 cups water, spring onion, garlic if used, oil and coriander or parsley (or a combination of the two if preferred). Bring to the boil, cover pan and simmer on low heat for 1 hour or until lentils are soft. Put water and flour in a screw top jar, seal and shake until thoroughly combined. This prevents lumps forming. Pour this gradually into boiling soup, stirring constantly, until thickened slightly. Add vinegar and salt and pepper to taste. Return to the boil, boil gently for 5 minutes, then serve hot.