Pat the Oxtail dry and season generously with Salt and Black Pepper. Heat a heavy-bottomed pot and brown the oxtail in batches in the Beef Dripping until deeply caramelized; transfer browned pieces to a plate.
Add the chopped Onion, Carrot, Celery and Leek to the pot and sweat gently until softened and starting to colour, about 8–10 minutes.
Stir in the Tomato Purée and sprinkle over the Plain Flour; cook for 2–3 minutes to remove the raw flour taste and coat the vegetables.
Pour in the Madeira and Worcestershire Sauce, scraping up the browned bits from the bottom of the pot to enrich the base.
Return the browned oxtail to the pot and cover with Water. Add the Bay Leaf, Thyme, Parsley Stalks, a few Black Peppercorns and a whole Clove. Bring to a gentle simmer, partially cover, and cook very slowly for 3–4 hours (or until the meat is tender and falling from the bone).
Skim off any excess fat or scum from the surface from time to time and adjust the heat to maintain a very low simmer.
When the oxtail is tender, remove the meat from the bones and shred or chop it; strain the broth if you prefer a clearer soup, then return the meat to the pot. If the broth is too thin, gently reduce it until it reaches the desired intensity.
Stir in a knob of Unsalted Butter to add shine and roundness, then taste and adjust seasoning with additional salt and pepper as needed.
Ladle the soup into bowls, scatter chopped Flat-Leaf Parsley over the top, and serve with crusty bread or mashed potatoes for dipping.
