Wash and debone the chicken drumsticks, then cut them into small 3 cm cubes.

Place the chicken in a large bowl and add the light soy sauce, dark soy sauce, oyster sauce, cornstarch, salt, and black pepper.

Mix well with your hands until every piece is evenly coated.

Cover with plastic wrap and marinate for 30 minutes. If you're short on time, marinate for at least 15–20 minutes.

While the chicken is marinating, prepare your vegetables.

Thinly slice the onion into strips.

Slice the lemon into thin rounds, and using a toothpick or the tip of a knife, carefully remove all the seeds.

Slice the bird's eye chilies into rings and roughly chop the cilantro. Set everything aside.

Place a large frying pan or skillet over medium-low heat and add a tablespoon of cooking oil.

Once the oil is hot, carefully add the marinated chicken pieces in a single layer, making sure not to overcrowd the pan. You may need to cook in batches.

Let the chicken cook undisturbed for about 2-3 minutes, until a golden-brown crust forms on one side.

Flip the pieces and continue to cook for another 2-3 minutes, until the other side is browned and the chicken is cooked through.

Add the onion slices and stir-fry for 1 minute until fragrant.

Finally, add the granulated sugar, chilies, lemon slices, and cilantro. Stir quickly so the chicken absorbs the spicy lemon flavor.