Cover the bottom of a small marmite with a layer of the usual sliced root vegetables and herbs and place on top 1½ kg (3 lb 6 oz) oxtail cut in sections. Cover with a lid and place in the oven to sweat for 15 minutes. Moisten with 2½ litres (4½ pt or 11 U.S. cups) stock made in advance from 1½ kg (3 lb 6 oz) gelatinous bones and 3¼ litres (5¾ pt or 7⅛ U.S. pt) water simmered continuously and gently for 7–8 hours.
Cook the oxtail gently for 3½–4 hours then remove the oxtail and reserve. Clarify the cooking liquor which has been skimmed and strained, with 500 g (1 lb 2 oz) finely chopped lean beef, 100 g (3½ oz) white of leek and 1 egg white; allow to cook gently for 1 hour and strain through a clean cloth.
Serve the clarified soup garnished with the cooked oxtail allowing 1 section per person and 200 g (7 oz) large Brunoise of carrot, turnip and celery cooked in butter and a little Bouillon until the liquid has evaporated.