Prepare the Bang Bang Sauce: In a medium bowl, combine the mayonnaise, Thai sweet chili sauce, Sriracha, and honey. Mix well until smooth and well-blended. Adjust the Sriracha according to your spice preference.
Marinate the Chicken: In a large bowl, whisk together the buttermilk, egg, and 1 tablespoon of Sriracha. Add the chicken tenderloins and coat them well. Cover and marinate in the refrigerator for at least 30 minutes, or up to 2 hours for best results.
Prepare the Coating: In a shallow dish, combine the all-purpose flour, cornstarch, garlic powder, kosher salt, black pepper, and cayenne pepper (if using). Mix until well combined. Place the panko breadcrumbs in a separate shallow dish.
Coat the Chicken: Remove the chicken from the buttermilk marinade, allowing the excess to drip off. Dredge each piece of chicken in the flour mixture, pressing lightly to adhere. Then dip the chicken back into the buttermilk marinade, and finally coat it in the panko breadcrumbs. Ensure each piece is well-covered for an extra crispy texture.
Fry the Chicken: Heat about 1 inch of canola oil in a large skillet over medium heat until it reaches 350°F (175°C). Fry the chicken tenderloins in batches, being careful not to overcrowd the pan. Cook for approximately 3 to 4 minutes on each side, or until the chicken is golden brown and fully cooked. Then, move the chicken to a plate lined with paper towels to absorb any excess oil.
Toss in Bang Bang Sauce: Once all the chicken is fried, gently toss the crispy chicken pieces in the prepared bang bang sauce until they are well-coated. Alternatively, you can serve the sauce on the side for dipping if you prefer to keep the chicken extra crispy.
Serve and Garnish: Transfer the coated chicken to a serving platter. Sprinkle with freshly chopped parsley to add a vibrant touch and enhance freshness. Serve immediately with extra bang bang sauce on the side if desired.