Prepare your pork belly by cutting it into one inch cubes and patting each piece dry.
In a mixing bowl, combine vinegar, soy sauce, garlic, onion, dark brown sugar, bay leaf, and peppercorns. Stir until the dark brown sugar dissolves.
In a glass container with an airtight lid, add the pork belly and pour the marinade over the meat. Turn the pieces to coat each piece evenly. Place the lid on top and marinate for one hour. (You can place it in the fridge for 40 minutes and place it on the counter the last 20 minutes to come to room temperature).
In a pot over medium-high heat, add the oil and transfer the pork belly pieces into the pot. Brown the pork belly on each side for about 30 seconds and turn. You want a slight browning, but not golden brown.
Add all the pieces of pork belly and marinade liquid into the pot. Add enough water so that it slightly covers the meat (about two to three cups) and bring to a boil.
Lower to medium heat and simmer for 20 minutes, covered.
Remove the lid and stir the contents. Raise the heat back to medium-high and cook uncovered for another 20 minutes.
Check the pork adobo by stirring around the meat, checking the tenderness of the meat, and taste the liquid for flavor. You can also use a strainer or spoon to skim the top if you have any extra fat or oil floating. (I would recommend skimming the oil on top if you are using pork belly to remove excess fat).
In the last 10 minutes, add in the boiled eggs to soak up the adobo sauce. The total cooking time from searing to braising to adding the eggs is around one hour.
Finished pork adobo should have tender meat, dark brown liquid, and have a strong vinegar flavor because it’s meant to be eaten with rice. If you want less of a vinegar taste, you can add more water in one tablespoon increments to dilute or you can also add more sugar to counteract the flavor.
Make sure to not overcook your meat or it will end up pulverized since pork belly has a lot of fat.
Adobo is supposed to have somewhat of a strong flavor because it’s meant to be eaten with rice.