In a Dutch Oven or wok over medium-high heat, heat oil until very hot.
Add the pork belly chunks in a single layer and cook for 2 to 3 minutes and lightly browned. Turn and cook for another 1 to 2 minutes or until all sides are crispy.
Remove pork belly from the pot and drain on paper towels.
In the pot, add onions and garlic and cook, stirring regularly, until softened.
Add pork belly chunks back to the pot and stir to combine.
Add pineapple juice and vinegar. Bring to a boil, uncovered and without stirring, for 3-5 minutes.
Add soy sauce, Worcestershire Sauce, water, peppercorns, and bay leaves. Stir to combine and bring to a boil.
Lower heat, cover, and simmer for 50 to 60 minutes, until pork pieces are tender and sauce has reduced.
Add brown sugar and stir to combine. Season with salt to taste. Continue to simmer until sauce is thickened.
Add pineapple chunks and cook for 1 minute until heated through.
Serve hot with steamed rice.