Cut the pork butt into large two-inch cubes.
Season the cubes of pork with Kosher salt all over.
Heat some vegetable oil in a large stock pot or Dutch oven.
Sear the pork cubes on high heat until golden-brown.
Add the white onion, celery, carrots, bay leaf, pork lard, and cover with sunflower seed oil.
When the oil is 170F, reduce the heat to low and allow the pork to cook slowly in the oil for roughly 8 hours, or until completely falling apart and tender.
When the pork is ready, remove the pork from the fat and set aside in a large mixing bowl while you prepare your sauce for the filling.
For a thin, North Carolina-style BBQ homemade sauce, mix together the ¾ cup ketchup with half a cup of apple cider vinegar and a few tablespoons of brown sugar in a small sauce pot on the stove.
Increase the heat to medium-low, and heat gently while stirring until the brown sugar has dissolved.
When the sugar is dissolved, remove the sauce from the heat, and season with Kosher salt to taste.
Add in the diced red onion to the sauce, and set aside for later.
Shred the pork in the large mixing bowl, and add in the BBQ sauce with the onions that you prepare earlier.
Add the chopped cilantro, if desired.
Taste the mixture, and add additional Kosher salt if desired.
When you are ready to serve, cut the bottom ends off the endives, and separate the larger Endive leaves from one another.
Arrange the individual endive leaves on a serving platter, and fill each one with a small scoop of the shredded pork mixture.
Serve immediately.