Marinate: In a large bowl, combine chicken, garlic, soy sauce, vinegar, peppercorns, and bay leaves. Marinate for at least 30 minutes.
Sear: Remove chicken from the marinade, reserving the liquid. Pat chicken dry and sear in hot oil in a pot until golden brown on all sides. Set chicken aside.
Simmer: Pour the reserved marinade into the pot. Bring to a boil and let it bubble for 2-3 minutes without stirring to cook off the harsh vinegar taste.
Braise: Return the chicken to the pot. Add water and optional brown sugar. Reduce heat to low, cover, and simmer for 40 minutes until the chicken is tender.
Reduce: Uncover the pot, increase heat to medium, and simmer for another 10-15 minutes to reduce the sauce until it becomes a thick glaze.
Serve: Let the adobo rest for 10 minutes before serving hot with steamed rice.