Prepare the liver: Soak the chicken livers in cold water for 5 minutes. Drain water and rinse with cold water. Set aside in a colander to remove excess moisture.
Make the adobo base: In a pot, combine soy sauce, vinegar, water, bay leaves, and peppercorns. Bring to a simmer over medium heat. Let it simmer for 3-5 minutes to mellow the acidity of the vinegar.
Cook the liver: Turn heat to low, and add liver one by one. Cook just until the liver turns opaque and no longer pink and becomes firm, about 5 minutes. Remove the livers from the sauce and continue to simmer until the sauce is reduced.
Prepare aromatics: In a skillet over medium heat, add oil then the garlic slivers. Stir once the oil becomes hot to prevent burning. Lower heat and fry the garlic just until golden and crispy, then remove from oil and set aside.
Build flavors: Cook the ginger in the same oil for several seconds until lightly browned. Add the onions and cook until soft and translucent.
Finish the dish: Add the chicken livers and cook until sides are nicely browned. Pour the reduced sauce over and simmer until it thickens. You can also cook it longer so that the sauce is almost completely reduced.
Final touch: Toss in the green chilis (if using) and then turn off the heat.
Serve: Transfer to a serving dish and top with the toasted garlic slivers.