In a large bowl, whisk together soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, minced garlic, grated ginger, and toasted sesame seeds until well combined. Add chicken thighs and coat well, then marinate in the refrigerator for at least 20 minutes.

In a separate mixing bowl, combine shredded cabbage and julienned carrot. In another bowl, whisk together mayonnaise, rice vinegar, sugar, salt, and pepper until smooth, then pour over the cabbage mixture and toss to combine. Cover and chill.

Heat a skillet over medium-high heat and cook the marinated chicken thighs for 6-7 minutes per side until charred and cooked through (internal temperature of 165°F). Let rest before slicing.

Butter the insides of sandwich buns, then toast them in the same skillet over medium heat until golden and crispy, about 2-3 minutes.

Layer the sliced chicken on the bottom half of the toasted bun, drizzle with extra Korean BBQ sauce, and top generously with cabbage slaw. Secure with the other half of the bun and serve.