Place the chicken in a bowl and add oyster sauce, soy sauce, sugar, and pepper. Mix thoroughly to coat every piece evenly. Let the chicken marinate for at least 30 minutes to allow the flavors to absorb.

In a separate bowl, combine all ingredients for the seasoned flour. In addition, prepare a bowl of cold water for the dredging process.

Lightly coat each marinated piece of chicken in the seasoned flour, making sure every surface is covered. Dip the floured chicken into cold water, careful not to scrub off the coating. Hold the chicken above the bowl for about 10 seconds to let the excess water drip off. Then dredge it again in the seasoned flour. Ensure the coating is even and consistent. For extra crispiness, you can repeat the dredge-dip-dredge method 3 to 4 times, using fresh cold water for each piece. After dredging, let the coated chicken rest for 5 minutes before frying.

Heat oil in a deep skillet over medium heat. Once the oil reaches frying temperature, gently lower the chicken into the pan. Fry for 20 to 25 minutes until the crust is golden and the chicken is thoroughly cooked. Transfer to a wire rack to drain any excess oil and maintain crispiness.

Add enough oil to lightly coat the base of a frying pan and heat over medium flame. Add the onion, garlic, serrano peppers, and Thai chili peppers. Sauté for 3 to 4 minutes, or until the onions begin to turn translucent. Add the tomato, cover, and let it cook for 1 to 2 minutes until softened. Uncover and sauté for another minute. Remove from heat and let the mixture cool slightly. Then, using a mortar and pestle or food processor, mash the mixture into a coarse sambal. Transfer to a bowl and season with salt and sugar. Stir to combine.

Use the back of a heavy knife or a pestle to gently smash the fried chicken to crack the crust and tenderize the meat. Serve the smashed chicken with sambal either on the side or spooned over the top. Complete the plate with steamed rice, fresh cabbage, and crisp cucumber slices.

Combine panko breadcrumbs with salt, pepper, garlic powder, paprika, and sugar. Press the marinated chicken into the breadcrumb mixture until thoroughly coated. Spray with cooking oil on all sides. Air fry at 375°F (190°C) for 15 to 20 minutes, flipping halfway through and spraying again after turning. Cook until golden and crispy.