Heat the oven to 325°F: Place an oven rack in the lower-middle of the oven.
Trim off any large pieces of fat from the outside, but leave small pieces and the interior fat. If using boneless pork, cut the pork into several large fist-sized pieces. If using bone-in, leave the pork as is, on the bone.
Season the pork with salt, pepper, and spices. Rub the seasoning into the pork with your fingers so the meat is evenly coated on all sides.
Optional to sear the pork. If time permits, searing will deepen the final flavour of the pork and give it some textural contrast. Warm the oil in the Dutch oven over medium-high heat. Sear the pork on all sides, working in batches as necessary so as not to crowd the pan.
Add the vegetables (if using). Add onions, garlic, and other vegetables to deepen the final flavour of the pork. If using, nestle them around the pork in the Dutch oven.
Pour the liquid (vegetable broth) over the top of the pork. The pork should be only partially submerged, with some of the pork remaining above the surface of the liquid.
Set the Dutch oven with the pork over medium-high heat and bring the liquid to a simmer.
Cover and transfer to the oven. Once simmering, cover the Dutch oven and transfer the whole pot to the oven. Cook for 2 to 4 hours, until fork tender. Let the pork cook undisturbed for 2 hours, then begin checking it every half hour. Total cooking time will be 2 to 4 hours, depending on the amount of pork and whether it's bone-in (which takes longer to cook).
The pork is done when the meat can be easily pierced with a fork without resistance, and easily falls apart with a little pressure. If cooking pork on the bone, the meat should be falling off the bone. If in doubt, cook the meat another half hour.
Lift the pieces of pork out of the liquid and transfer to a large mixing bowl. When cool enough to handle, use two forks or your fingers to shred the meat into pieces. Remove any large pieces of fat or bones.
Strain the cooking liquid into a measuring cup. The vegetables can be chopped and mixed in with the pork, if desired. Skim the fat off the top of the cooking liquid.
Moisten the pork with cooking liquid or barbecue sauce (optional). For more moist and flavourful pulled pork, mix some of the cooking liquid back into the pork. Start with a little, mix, then add more until the pork is as wet or dry as you like. Alternatively, for barbecue pulled pork, you can mix in barbecue sauce.
Pulled pork will keep for 1 week in the refrigerator or for up to 3 months in the freezer.