In a medium bowl, combine gochujang, soy sauce, honey, sesame oil, minced garlic, grated ginger, rice vinegar, and black pepper. Whisk until smooth.

Take the chicken thighs and place them in a resealable bag. Pour the marinade over the chicken, ensuring each piece is thoroughly coated. Seal the bag or cover the bowl and refrigerate for at least 1 hour, preferably overnight.

In a large bowl, combine the finely shredded green cabbage and julienned carrots. Stir well to evenly distribute the vegetables.

In a separate bowl, whisk together mayonnaise, lime juice, and sriracha. Pour the dressing over the cabbage and carrots, then toss until well-coated.

Preheat a grill pan or skillet over medium-high heat and add a light coat of oil.

Carefully place the marinated chicken thighs onto the hot grill. Cook for about 6-7 minutes per side, until charred and cooked through (internal temperature of 165°F). Let the chicken rest for a few minutes.

Slice the chicken into strips.

Slice the brioche buns and toast them until golden brown.

Layer the bottom half of the toasted bun with sliced chicken, and top with crispy slaw. Sprinkle with fresh cilantro and sesame seeds, then cap with the top half of the bun.