In a large bowl, whisk together soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, minced garlic, and grated ginger until well combined. Add chicken thighs, ensuring they are coated and marinate at room temperature for at least 20 minutes or refrigerate for up to 2 hours.

In a mixing bowl, combine grated cabbage and julienned carrots. In a separate bowl, whisk together mayonnaise, rice vinegar, sugar, salt, and pepper until smooth. Drizzle over cabbage mixture, toss well, 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 per side or until cooked through and nicely charred. Let rest before slicing.

Butter each half of the buns and toast in a skillet over medium heat until golden brown and crisp.

Assemble sandwiches by placing sliced chicken on bun bottoms, drizzling with marinade if desired, topping with slaw, and placing the top bun over.