Start by preparing the Boom Boom sauce. In a medium-sized bowl, whisk together mayonnaise, honey, sweet chili sauce, Sriracha hot sauce, and buttermilk until combined. Add in the egg and season generously with salt and pepper. Whisk to combine once more. Set aside for later use.
In a separate bowl, mix together the cornstarch and all-purpose flour. Add in some salt and pepper to season. Place the cubed chicken breast into the flour mixture and coat each piece evenly with the dry ingredients. Once all of your chicken is coated, place it onto a wire rack set over a baking sheet.
Preheat vegetable oil in a large saucepan or skillet over medium heat until it reaches 350°F (175°C). Working in batches, fry the chicken for 5-7 minutes or until golden brown and crispy. Transfer the cooked chicken to a plate lined with paper towels to absorb any excess oil.
When all of the chicken is cooked, return it to the saucepan and pour in the Boom Boom sauce. Toss to fully coat each piece with the sauce.
Sprinkle panko breadcrumbs over top and gently toss them once more. Serve your Boom Boom chicken immediately while hot and crispy.