Pat dry then lightly salt and heavily pepper the chicken. Heat the oil in a large soup pan or Dutch oven over medium heat. Add the chicken, skin-side down, working in batches so as not to over-crowd the pan. Cook until golden brown, about 10 minutes. Transfer the chicken to a plate.
Add the garlic and jalapeños to the hot oil and cook for 30 seconds or until fragrant. Add the vinegar, tamari, bay leaves, and brown sugar. Bring to a boil, then reduce the heat to simmer. Add the chicken back to the pot, skin-side up. Cover the pan and cook until the chicken is tender and just staring to pull away from the bones, 35-40 minutes.
Transfer the chicken to a clean plate and remove the bay leaves. Turn the heat up under the pot and bring the sauce to a boil. Let boil, uncovered, until the sauce starts to thicken, 5-7 minutes. Put the chicken back in the pot, turning to coat with the sauce.