In a large pot, brown the pork in the oil. Season with salt and pepper. Add the remaining ingredients. Add broth, if needed, to cover. Bring to a boil. Cover and simmer gently for 2 hours and 30 minutes to 3 hours, depending on the cut of meat, until the meat is fork-tender. Strain the broth through a sieve and return to the pot. You'll need 1.5 litres (6 cups) of liquid. If necessary, add chicken broth. Set aside. Discard the vegetables.