Heat 1 tbsp of cooking oil in a pot.
Remove the pork from the marinade and place into the pot.
Brown the pork for 2 minutes each. Don’t cook pork all the way through. Reserve the marinade.
Remove pork from the pot and set aside in a bowl.
Heat the remaining oil (1 tbsp) in the same pot.
Add onions and garlic. Saute for 1-2 minutes until fragrant.
Place the pork back into the pot and add the reserved marinade.
Add water, brown sugar and whole peppercorns.
Turn the heat up to high, cover the pot and bring to a boil. Boil for 2 minutes.
Turn the heat down and simmer covered for 45 minutes or until the pork becomes tender.
Add vinegar.
Stir and continue to cook for 5 minutes.
Turn the heat off.
Serve hot with steamed rice.