Mix the rice vinegar, soy sauce, ginger, garlic, salt and pepper in a sealable plastic bag. Shake to mix well. Add the chicken pieces. Marinate for at least 20 minutes or overnight.

In another sealable plastic bag, mix the flour, cornstarch, and baking powder.

Transfer the chicken pieces into the flour bag (first shaking off excess marinade).

Shake the bag to completely coat the chicken, then place the bag in the refrigerator for 20 minutes.

Meanwhile, combine all sauce ingredients in a saucepan over medium heat. Stir well and simmer for 5 minutes to thicken slightly.

After 20 minutes, remove the chicken from the refrigerator. Shake the bag again to coat the chicken with flour.

Preheat the air fryer at 400ºF (200ºC) for 5 minutes.

Spray the basket well with cooking oil. Transfer the chicken pieces to the air fryer basket, not touching if possible. Spritz the chicken pieces with oil so that there isn’t any dry spots.

Air fry for 8 minutes. Carefully turn the chicken pieces over so that you don’t know the coating off, spritz with more oil, and cook for another 5-7 minutes. The amount of time it takes will vary based on your air fryer and the size of the chicken pieces.

When the chicken reaches an internal temperature of 165° F(75°C), transfer it to a bowl and toss to coat with the sauce.

Steam the bao in a steamer basket over a pot of boiling water or steam it in the microwave according to package instructions.

Assemble the bao with chicken, onion, and cucumber.