1) In a large mixing bowl, whisk together the tomato puree, cider vinegar, Worcestershire sauce, paprika and dried herbs. Set aside.
2) Season the short ribs with 1 tablespoon of the salt. Place a large griddle over medium-high heat and once a drop of water bounces off, sear the meat until browned on all sides. Once browned, remove the meat to the bowl with the paste and toss to coat. Transfer to a large piece of heavy-duty aluminium foil and seal tightly. Place the package into a metal tin and put into a cold oven on the middle rack. Set the oven to 115C/Gas 1 and cook for 4 hours.
3) Remove the meat from the oven and carefully poke a hole in the pack while holding it over a heatproof container. Drain the liquid into the container and place it into the refrigerator to cool enough so that the fat separates from the rest of the liquid, approximately 1 hour. After 1 hour, transfer the liquid to the freezer and keep there until the fat cap has solidified, approximately 1 hour.
4) Allow the ribs to sit at room temperature whilst the liquid is cooling or if serving the next day, place in the refrigerator until ready to finish.
5) Retrieve the liquid from the refrigerator and remove the fat cap that has formed on top. Measure out 1 tablespoon of the fat and reserve the rest for another time. Place the fat into a large saucier and place over medium heat. Once the fat has melted add the onion along with the remaining teaspoon of salt and stir to separate the onions into rings. Allow to cook for 2 to 3 minutes, stirring occasionally.
6) Add the potatoes along with a pinch of black pepper and stir to combine. Next, add the liquid reserved from the meat and stir. Cover tightly and decrease the heat to low so that no heat is escaping the lid. Cook for 30 minutes or until the potatoes are fork tender.
7) Meanwhile, cut the meat away from the bone, removing the connective tissue and discarding. Once the potatoes are tender, uncover and set the meat atop the vegetables. Cover and continue to cook for 10 minutes. Serve sprinkled with the parsley.