Cut the chicken breasts into uniform 1-inch pieces. Place them in a medium bowl, cover completely with buttermilk, and refrigerate for at least 30 minutes (up to 4 hours for extra tender results).

While the chicken marinates, whisk together flour, garlic powder, onion powder, paprika, salt, and black pepper in a large bowl until well combined.

In a separate small bowl, combine mayonnaise, sweet chili sauce, sriracha, lime juice, and honey until smooth. Taste and adjust sriracha to your preference. Set sauce aside.

Remove chicken from buttermilk, allowing excess to drip off. Dredge each piece thoroughly in the flour mixture, pressing gently to help coating stick. Place coated pieces on a wire rack and let rest for 10 minutes - this helps the coating bond to the chicken.

Heat vegetable oil in a large skillet over medium-high heat until it reaches 350°F (175°C). Use a thermometer for accuracy and adjust heat as needed to maintain this temperature throughout cooking.

Carefully add 4-5 chicken pieces at a time (don't overcrowd), and fry for 4-5 minutes per side until deep golden brown and crispy. The internal temperature should reach 165°F (75°C). Transfer to paper towel-lined plates to drain excess oil and repeat with remaining chicken.

Arrange the crispy chicken on a serving platter and drizzle generously with Bang Bang sauce, or serve the sauce on the side for dipping. Garnish with chopped green onions and sesame seeds.