In a medium bowl, whisk together soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, minced garlic, and grated ginger until smooth. Add boneless chicken thighs, coat well, cover, and marinate in the fridge for at least 20 minutes.

In a large mixing bowl, combine shredded cabbage and julienned carrot. In a separate bowl, whisk together mayonnaise, sugar, salt, and pepper. Pour dressing over cabbage mixture and toss until combined. Chill in the fridge.

Preheat a skillet over medium-high heat and add oil. Cook marinated chicken for 6-7 minutes on each side until charred and internal temperature is 165°F. Let it rest for 5 minutes before slicing.

Spread butter on cut sides of the buns and toast them in a skillet until golden brown and crispy.

On the bottom half of each toasted bun, layer sliced chicken, drizzle extra BBQ sauce if desired, and top generously with cabbage slaw. Place the top half of the bun on and serve immediately.