1. Put the onion, carrots, leek, parsnip and garlic in a large, heavy saucepan with 284ml/½ pint of the chicken stock. Cover the pan and bring to the boil. Continue boiling for 5-10 minutes, then uncover the pan, reduce the heat and simmer gently over a low heat for about 20 minutes, until the vegetables are tender and syrupy.
2. Stir in the lentils and cook over a low heat gently for 2 minutes, then add the remaining stock, the canned tomatoes and herbs. Simmer gently for about 45 minutes, until the soup thickens and the flavours amalgamate.
3. Season to taste, and remove the bay leaf and herb sprigs. If wished, cool thoroughly and freeze, then defrost and reheat at a later date. Serve hot, sprinkled with parsley.