Marinate the Chicken: Place the chicken pieces in a bowl with buttermilk and let them soak for at least 30 minutes. This helps tenderize the chicken and keeps it juicy.
Prepare the Coating: In a separate bowl, mix flour, cornstarch, garlic powder, onion powder, paprika, salt, and black pepper. Whisk an egg into the marinated chicken to help the breading stick.
Coat and Fry: Heat vegetable oil in a deep pan to 350°F (175°C). Dredge each piece of chicken in the flour mixture, shaking off excess, and fry until golden brown and crispy (about 4-5 minutes). Drain on paper towels.
Make the Sauce: In a small bowl, whisk together mayonnaise, sweet chili sauce, sriracha, honey, and rice vinegar until smooth.
Toss and Serve: Coat the crispy chicken in the Bang Bang sauce or drizzle it on top. Garnish with chopped green onions or sesame seeds for an extra pop of flavor.