Heat the vegetable oil in a large pot over medium-high heat.
Add the pork shoulder pieces and cook until browned on all sides.
Add the chopped onion, minced garlic, and minced ginger. Cook until the onion is softened and translucent, about 5 minutes.
Pour in the vinegar and let it boil for about 2-3 minutes to reduce the strong vinegar smell.
Add the beef or chicken broth, soy sauce, bay leaves, ground black pepper, and salt. Stir well to combine.
Reduce the heat to low, cover, and simmer for 1-1.5 hours, or until the pork is tender.
Slowly stir in the pork blood (if using) and cook for another 10-15 minutes, stirring frequently until the sauce thickens and becomes rich and dark.
If using, add sliced green chili peppers for additional heat and cook for an additional 5 minutes.
Adjust seasoning with salt, pepper, and sugar if needed.
Enjoy your meal!