Dice the onion very finely and set it aside. Pour the olive oil and add the onion, and the red pepper flakes into a Dutch oven casserole. Sauté the onion until translucent on medium heat and stir constantly to prevent burning.
Cut the beef shin into chunks and set aside. *Pat the meat cuts with a paper towel to achieve better browning.
Start by adding the pork belly and the beef shin into the casserole. Brown all the meats on every side on medium heat. Once done, remove the meats and add them to a bowl.
Add the sausages and the ground pork on medium heat in the same casserole. Brown the meats and breaks up the ground pork with a wooden spoon.
Add back the pork belly and the beef shin into the casserole, along with any juices left in the bowl. Cook over medium heat for 5 minutes to flavor up. Stir constantly.
Pour the wine into the casserole. With a wooden spoon stir and scrape any meat bits to the bottom. Cook over medium heat.
Once the alcohol is evaporated add the San Marzano, the herbs, and salt. Stir and leave to cook for 2 minutes on medium heat.
Add the passata and give a quick stir. Turn to low heat and let cook the calabrese sauce for 1 hour. Cover the casserole and stir often.
After 1 hour add the water and adjust the seasoning. Stir and cook for another 30 minutes on low heat. Stir often.