Remove the Oxtail from its packaging, untie it, pat it dry and generously season it with salt.
Place a large casserole dish over a high heat. Dollop in the beef dripping. Once smoking hot and sizzling, add the oxtail. You may need to do this in batches depending on the size of your pan. Brown the oxtail all over until it is beautifully caramelised, then remove from the pan and set to one side.
Turn the heat down and to the same pan add a knob of butter along with the onions, celery, carrots, garlic and herbs and a small pinch of sea salt. Cook the veg until the onions have become translucent and the carrots and celery have softened, this may take around 7-8 minutes.
To the veg add the tomato purée, umami paste and Worcestershire sauce and give everything a good stir. Turn the heat up slightly and pour in the wine, allowing it to bubble for a few minutes.
Return the oxtail to the pan and pour in the stock. Bring to the boil, then turn down the heat down to a gentle simmer. Cover and cook for 3 hours, until the oxtail is tender and falling off the bone. Add the pepper and check the seasoning.
Using a slotted spoon, remove the oxtail from the pan and transfer it to a plate to cool.
Once the oxtail has cooled, shred the meat into a bowl, discarding the bones (or give them to the dog) and place in the fridge.
Strain the cooking liquor through a sieve into a bowl and leave in the fridge overnight.
The next day, scrape away and discard the layer of fat on top of the cooking liquid. Spoon the jellified soup into a pan and heat through until simmering.
In a small bowl, mix the flour and a couple of tablespoons of the hot soup until it forms a smooth paste. Whisk the paste into the soup and simmer for two minutes. Add the shredded oxtail meat to the pan and heat through for a minute or two before serving.