Prepare the chicken feet. Trim the nails and rinse the chicken feet thoroughly. Boil for 5 minutes to remove impurities, then drain and set aside.
Fry the chicken feet. Heat 3 tablespoons oil in a pot over medium heat. Fry the chicken feet until lightly browned, then remove and set aside. This step adds deeper flavor to the dish.
Sauté aromatics. In the same pot, heat 2 tablespoons oil. Sauté garlic and onion until fragrant and soft.
Simmer the adobo. Add fried chicken feet, soy sauce, water, whole peppercorns, sugar, and potatoes. Bring to a boil, then lower heat and simmer for 20–30 minutes until chicken feet and potatoes are tender. Add water if needed.
Add vinegar. Pour in vinegar but do not stir. Let it cook for 5 minutes uncovered to mellow the sharpness.
Final touches. Stir everything together. Add oyster sauce, long green chilies, and red chili. Season with salt and pepper. Simmer 2–3 more minutes until the flavors combine.
Serve & enjoy. Transfer to a plate and serve hot with steamed rice or as pulutan.