In a mixing bowl, combine gochujang, soy sauce, honey, sesame oil, minced garlic, grated ginger, rice vinegar, and black pepper. Whisk to form a smooth marinade.

Place the chicken thighs in a bag or dish and pour the marinade over to coat. Refrigerate for at least one hour, preferably overnight.

For the slaw, mix shredded cabbage and julienned carrots in a large bowl until well combined.

In another bowl, whisk mayonnaise, lime juice, and sriracha (if using). Mix this dressing into the cabbage and carrots, coating the slaw.

Heat a grill pan over medium-high and lightly oil the surface. The pan is ready when hot.

Cook the marinated chicken for 6–7 minutes on each side or until done (internal temperature of 165°F).

Let the chicken rest for 5 minutes, then slice into strips.

Toast the brioche buns until golden brown.

Assemble the sandwiches by layering chicken on the bottom bun, topping with slaw and garnishing with cilantro and sesame seeds.