Begin by cutting the chicken breasts into bite-sized pieces, ensuring that all pieces are uniform for even cooking.

In a mixing bowl, combine the cornstarch, salt, black pepper, garlic powder, and onion powder. Mix well to create the coating for the chicken.

Toss the chicken pieces in the cornstarch mixture until they are well-coated, shaking off any excess.

In a large skillet, heat the vegetable oil over medium-high heat. Once hot, add the coated chicken pieces in a single layer, ensuring they do not overcrowd the pan.

Cook the chicken for about 4-5 minutes on each side or until golden brown and crispy. You may need to do this in batches to avoid steaming the chicken.

While the chicken is cooking, prepare the bang bang sauce by combining the mayonnaise, sweet chili sauce, sriracha, rice vinegar, and sesame oil in a bowl. Stir until smooth and well-blended.

Once the chicken is cooked, transfer it to a paper towel-lined plate to absorb excess oil.

In a large mixing bowl, toss the crispy chicken pieces with the prepared bang bang sauce until they are evenly coated.

Serve the bang bang chicken garnished with sliced green onions and a sprinkle of sesame seeds. Enjoy it warm as an appetizer or main dish.