Joint the chicken: cut the legs and wings from the body, remove the breast bone, and cut the backside in half. Dice vegetables and onions and chop parsley.
Heat the oil in a large saucepan and fry the chicken joints in batches, until browned. Add all vegetables, except the leeks and parsley. Add the tomato whole, season with salt and pepper and cover with water.
Cover and simmer for at least 2 hours over a low heat. After 2 hours, add the leek and parsley and cook for a further 10 minutes.
Remove the chicken and let cool until cold enough to handle. Remove the skin and bones and chop the meat. Add as much meat to the soup as you like and keep the leftovers for another recipe.
Skim off the fat, heat soup up again and serve.
This recipe calls for soup vegetables. In this soup, fresh vegetables such as carrots, leeks, celery and parsley root work great. Parsnip can be used in place of parsley root.