In a bowl, combine the pork pieces with soy sauce and crushed garlic.
Allow the pork to marinate for about 30 minutes.
Heat cooking oil in a large pan over medium heat.
Add sliced onions and cook until they become soft and fragrant.
Add the marinated pork and cook for about 5–7 minutes until lightly browned.
Pour in the remaining marinade and add vinegar and water.
Add bay leaves and black peppercorns.
Bring the mixture to a boil, then reduce the heat.
Cover the pan and simmer for about 35–40 minutes until the pork becomes tender.
Stir occasionally and allow the sauce to reduce and thicken slightly.
Add sugar if desired to balance the flavor.
Taste and adjust seasoning if needed.
Serve hot with steamed rice.