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, cover and let marinate for 20 minutes at room temperature, or refrigerate for up to 2 hours for deeper flavor.

While the chicken marinates, make the slaw by combining cabbage and carrot in a large bowl. In a separate bowl, whisk together mayonnaise, rice vinegar, sugar, salt, and pepper. Drizzle dressing over cabbage mixture and toss. Cover and chill for at least 15 minutes.

Heat a skillet or grill pan over medium-high heat. Remove chicken from marinade and cook for 6-7 minutes on each side, or until cooked through and caramelized. Let it rest before slicing.

Spread butter on the cut sides of each bun. Toast in a non-stick skillet over medium heat until golden brown, about 2-3 minutes.

Assemble the sandwich with sliced chicken on the bottom half of the bun, drizzle with extra marinade if desired, add the zesty cabbage slaw, and top with the other half of the bun.