Start by preparing the spicy sauce. In a small bowl, combine mayonnaise, gochujang, honey, rice vinegar, sesame oil, and soy sauce. Mix well and set aside.
Place the chicken thighs between two sheets of plastic wrap and pound them to an even thickness of about ½ inch.
In three separate shallow dishes, set up your breading station: In the first dish, add the flour, garlic powder, onion powder, paprika, salt, black pepper, and cayenne pepper. Mix well.
In the second dish, beat the eggs.
In the third dish, add the panko breadcrumbs.
Coat each chicken thigh in the flour mixture, shaking off any excess. Then dip it into the beaten eggs, allowing any excess to drip off. Finally, coat the chicken in the panko breadcrumbs, pressing gently to adhere.
In a large skillet, heat the vegetable oil over medium-high heat. Once hot, carefully add the breaded chicken thighs.
Fry for about 4-5 minutes on each side or until golden brown and cooked through (internal temperature should reach 165°F).
Once cooked, transfer the chicken to a paper towel-lined plate to drain excess oil. Allow to cool for a minute before slicing.
Serve the chicken katsu drizzled with the spicy sauce. Enjoy with steamed rice and a side of pickled vegetables if desired.