In a bowl, whisk together the soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, minced garlic, and grated ginger until well combined. Add the chicken thighs, ensuring they are fully coated. Cover with plastic wrap and refrigerate for at least 20 minutes, up to 2 hours.

While the chicken marinates, mix the shredded cabbage and julienned carrots in a large bowl. In a separate bowl, whisk together the mayonnaise, rice vinegar, sugar, salt, and pepper. Pour over the cabbage and carrots, mixing well, and chill in the fridge for about 15 minutes.

Heat a grill or skillet over medium-high heat. Cook the marinated chicken thighs for 6-7 minutes on each side until fully cooked.

While the chicken rests, spread butter on the cut sides of each bun and toast in a skillet over medium heat for 2-3 minutes.

To assemble, start with the bottom bun, layer on sliced chicken, drizzle with reserved marinade if desired, top with the cabbage slaw, and finish with the top bun.