Preheat the oven to 160°C/320°F. Heat half the oil in a large saucepan with the onion, garlic, salt, pepper and chilli over medium heat for about 15 minutes. Reduce heat and add the rest of the oil and fresh tomatoes and cook for another 15 minutes. Add the tinned tomatoes and bring to a simmer for another 10 minutes or so until the sauce has begun to reduce.
While the sauce is cooking thoroughly cover the pork joint in salt and pepper. Heat the oil over a medium-high heat and then brown the pork all over.
Once the sauce is made and the meat has been browned place the pork into the sauce and place in the oven, covered, for 2-3 hours until the pork is falling apart.
Shred the pork and stir into the sauce. Serve over pasta, polenta or gnocchi and top with grated parmesan if desired.