Prepare the Bang Bang Sauce : In a medium bowl, combine mayonnaise, Thai sweet chili sauce, Sriracha, and honey. Mix until smooth and creamy. Adjust spice levels with extra Sriracha, if desired. Set the sauce aside or refrigerate until ready to serve.

Marinate the Chicken : In a large bowl, add chicken tenderloins and buttermilk. Cover and refrigerate for at least 20 minutes (or up to 4 hours) to tenderize the chicken.

Create the Coating : In a shallow bowl, mix flour, cornstarch, garlic powder, salt, black pepper, and cayenne pepper (if using). In another bowl, whisk together the egg and Sriracha. Place the panko breadcrumbs in a third bowl.

Coat the Chicken : Remove chicken from the buttermilk and let excess drip off. Dredge each piece in the flour mixture, then dip into the egg mixture, and finally coat with panko breadcrumbs. Press the breadcrumbs gently to adhere.

Fry the Chicken : Heat about 1-2 inches of canola oil in a large skillet over medium heat until it reaches 350°F (175°C). Fry the chicken in batches, avoiding overcrowding, for 3-4 minutes per side or until golden brown and fully cooked. Remove and place on a paper towel-lined plate to drain excess oil.

Toss and Serve : In a large bowl, toss the crispy chicken pieces with the Bang Bang sauce until evenly coated. Garnish with chopped parsley and serve immediately.