Prep your chicken. If you have wings, make sure to separate the pieces between the flat and the drumstick to make for easier cooking.
In a mixing bowl, combine the vinegar, soy sauce, minced garlic, bay leaf, and peppercorns. Add the chicken and mix so that each piece is covered with the marinade. Transfer chicken and marinade sauce into an airtight container and place it in the fridge for at least 3 hours. The longer you marinade, the better the flavor is infused into the chicken. The best chicken adobo I’ve had was marinated overnight.
Move the chicken from the fridge to the counter about 20-30 minutes before cooking.
Heat a pot over medium heat and add the vegetable oil. Brown the chicken for about one minute on each side or until the skin turns a light brown. If you can’t brown the chicken at the same time, you can do this in batches and transfer the browned pieces on a plate and set aside.
After browning the pieces, place all the chicken into the pot and add the leftover marinating liquid (don’t forget the bay leaf).
Add the water and dark brown sugar into the pot and stir. The water level should be right where the top of the chicken reaches, but not above the chicken.
Raise the heat to medium-high (320 °F) and bring the liquid to a boil for about ten seconds and then lower the heat medium-low (260 °F) so that it simmers. Cover with the lid and simmer for 20 minutes.
Remove the lid, stir the contents, and bring the heat up back to medium (300 °F) heat uncovered to reduce the liquid for another 20 minutes.
Check the temperature of the chicken to make sure it reaches 160 °F. Taste test and adjust the soup based on your preference, it should be very savory, tangy, and have enough saltiness. Remember this is meant to be eaten with rice to balance it out. Tips: If your chicken adobo is too salty, add one tablespoon of water to dilute at a time and taste again. If your chicken adobo is too tangy or has too much vinegar flavor for your liking, try adding one teaspoon of dark brown sugar and taste again.