Step 1: Marinate the Chicken

1. Place the chicken pieces in a bowl and pour the buttermilk over them. Stir to coat, cover the bowl, and let it marinate in the refrigerator for at least 20 minutes. Marinating helps tenderize the chicken and enhances its flavor.

Step 2: Prepare the Coating

1. In a shallow dish, whisk together the flour, cornstarch, garlic powder, paprika, salt, and black pepper.

Step 3: Heat the Oil

1. Pour oil into a deep skillet or Dutch oven, filling it about 2 inches deep. Heat the oil over medium heat until it reaches 350°F (175°C). Use a kitchen thermometer to ensure the oil is at the correct temperature for frying.

Step 4: Coat the Chicken

1. Remove the chicken pieces from the buttermilk, letting the excess drip off. Dredge each piece in the flour mixture, pressing lightly to ensure an even coating. Place the coated chicken on a wire rack or plate while you finish coating the rest.

Step 5: Fry the Chicken

1. Working in batches, carefully place the coated chicken pieces into the hot oil. Fry for 4-5 minutes, turning occasionally, until golden brown and cooked through. The internal temperature should reach 165°F (74°C).
2. Remove the chicken from the oil with a slotted spoon and place it on a paper towel-lined plate to drain excess oil.

Step 6: Make the Bang Bang Sauce

1. In a small bowl, whisk together the mayonnaise, sweet chili sauce, sriracha, honey, and rice vinegar (if using). Taste and adjust the seasoning as needed, adding more chili sauce or sriracha for extra heat.

Step 7: Toss the Chicken in Sauce

1. Place the fried chicken pieces in a large bowl. Pour the Bang Bang sauce over the chicken and gently toss until evenly coated.

Step 8: Garnish and Serve

1. Transfer the saucy chicken to a serving platter. Garnish with green onions, sesame seeds, or chopped cilantro. Serve immediately with lime wedges on the side for an extra pop of freshness.