In a bowl, soak the chicken pieces in buttermilk for at least 30 minutes.
In another bowl, mix flour, cornstarch, garlic powder, paprika, salt, and pepper.
Heat vegetable oil in a deep pan to 350°F (175°C).
Dredge each piece of chicken in the flour mixture, ensuring it's fully coated.
Fry in batches for about 3-4 minutes per side until golden brown and crispy.
Drain on a paper towel-lined plate.
In a separate bowl, whisk together mayonnaise, sweet chili sauce, honey, sriracha, and lime juice.
Toss the crispy chicken in the Bang Bang sauce until well coated.
Garnish with green onions and sesame seeds before serving.