Season the cleaned chicken with garlic powder and black pepper. Heat the vegetable oil in a large stockpot over medium high heat. Add the chicken legs into the pot and sear on each side for 2-3 minutes until they are golden brown.
Remove the chicken from the pot and add in the thinly sliced onions. Saute the onions for about 5 minutes, just until they begin to soften. Next add in the minced garlic and saute it with the onions for 1-2 minutes, stirring constantly so that it doesn’t burn.
Now pour the vinegar, soy sauce, and water into the pot with the onions and garlic. Use a wooden spoon to stir everything until it is fully incorporated. Scrape the bottom of the pot to get any bits and pieces off.
Next add in the brown sugar, the whole peppercorns, and the bay leaves and stir everything together. Now gently add your chicken legs back into the pot. Make sure that the chicken is fully covered with the adobo liquid.
Cover the pot with a lid and turn the heat down to medium-low. Allow the chicken to simmer for 30 minutes, uncover and make sure the liquid is still at a good level, if not, add about ¼ cup of water.
Gently stir the chicken and cover the pot and allow the chicken to simmer for another 15 minutes. The chicken should fall-off-the-bone tender, and the liquid should be nice and caramelized (thickened) by this time.
Serve immediately over rice and garnish with chopped green onions, and enjoy!