In a medium 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 the chicken thighs, ensuring they're fully coated in the marinade. Cover and let them marinate in the refrigerator for at least 20 minutes.

In a large bowl, combine shredded green and red cabbages along with julienned carrots. In a separate bowl, whisk together mayonnaise, rice vinegar, a pinch of sugar, salt, and pepper to taste. Pour this dressing over the cabbage mixture and toss until coated.

Heat a cast-iron skillet or grill pan over medium-high heat. Once hot, place the marinated chicken thighs in the skillet, cooking for about 6-7 minutes on each side until cooked through. Let it rest for 5 minutes.

Butter the inner sides of the brioche or potato buns and toast them butter-side down in the skillet for 2-4 minutes until golden brown.

Layer the sandwich by placing the sliced chicken on the bottom bun, drizzle with optional BBQ sauce, add cabbage slaw, and top with the other half of the bun.