Remove the oxtail from your marinade. Heat half of the oil in your stock pot over a high heat and brown the oxtails in batches. Brown each face of the oxtail for a few seconds, turning frequently and place in a bowl once browned
In the same pot, over the same high heat, add the rest of your oil and fry the chopped vegetable for a couple of minutes stirring frequently. Reduce the heat to medium high
Add the tomato puree and cook for 1 minute, stirring frequently
Add the wine that you marinated the oxtails in and reduce by about half. Make sure you scrape the pot to deglaze all those delicious flavours
Return the browned oxtail and any juices to the pot. Add the stock, bring to a slow simmer and reduce the heat to low. Cook the oxtails for 2½-3 hours on the lowest simmer possible. Partially cover the pan and stir occasionally
When tender, remove the oxtail with a slotted spoon and place to the side to cool
Strain the liquid from the pot and leave to cool then cover and place in the fridge overnight. Discard the vegetables
Once cooled enough to handle, strip as much meat as possible from the oxtail. Cut or pull into small pieces, cover and store in the fridge
The next day, using a large spoon, skim off the fat from the soup and discard
Place the chilled soup into your clean stock pot (it will be thick and gelatinous) and warm over a medium high heat. Once simmering, add the finely cut oxtail and carrot. Return to a simmer and on a low heat, cook for 10 minutes