Heat 2 tablespoons oil in a large nonstick skillet over high heat. Pat chicken very dry. Sear both sides for about 3 minutes per side, until lightly browned (do not cook through). Transfer to a plate and reduce heat to low.
Add remaining 1 tablespoon oil to the skillet. Add garlic, jalapeño (if using), and black pepper. Cook, stirring constantly, for about 45 seconds, until fragrant and just lightly golden. Do not let the garlic brown.
Pour in soy sauce, water, rice vinegar, oyster sauce, brown sugar, and bay leaves. Increase heat to high and bring to a simmer, then reduce to medium-high and simmer for 5 minutes.
Reduce heat to medium. Return chicken to the skillet in one even layer (smooth side down), along with any juices left behind on the plate. Simmer, uncovered, for 15 minutes. Do not stir, but check occasionally to make sure the liquid is not boiling too rapidly. If it is, lower the heat.
After 15 minutes, flip the chicken and cook another 5 to 10 minutes, or until the sauce is mostly reduced and glossy enough to coat the chicken. If the sauce is still watery, remove chicken to a plate and simmer the sauce over high heat until thickened. Return chicken and toss to coat in the glaze.
Add the chicken over rice and spoon the sauce on top, adding it slowly and to taste (it's salty!). Garnish with green onions if desired.
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Notes
Note 1: My friend uses a whole head of garlic. I like a little less, but feel free to use more or less to taste.Note 2: Do not use chicken breasts. The fat in thighs is needed for the sauce to reduce into a rich glaze.Storage: Store cooled chicken and sauce in an airtight container in the fridge for up to 3 days. Reheat gently on the stovetop or in the microwave, adding a splash of water if needed.