Marinate the Chicken: In a medium bowl, whisk together soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, minced garlic, and grated ginger until well combined. Add the chicken thighs, coat thoroughly, cover, and marinate at room temperature for at least 20 minutes or refrigerate for up to 2 hours.

Prepare the Cabbage Slaw: Combine shredded green and red cabbage and julienned carrots in a large bowl. In another bowl, whisk together mayonnaise, rice vinegar, sugar, salt, and pepper to create the dressing. Pour over the cabbage mixture and toss to coat. Refrigerate.

Cook the Chicken: Heat a skillet or grill pan over medium-high heat. Cook marinated chicken for 6-7 minutes on each side until charred and internal temperature reaches 165°F. Let rest for 5 minutes before slicing.

Toast the Buns: Butter the split sides of the buns and toast them in the skillet over medium heat for about 2-3 minutes until golden brown.

Assemble the Sandwich: Layer grilled chicken on the bottom half of each bun, drizzle with BBQ sauce if desired, and top with cabbage slaw. Place the bun top on and serve.