Whisk together soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, minced garlic, and grated ginger in a mixing bowl to create the marinade. Add chicken thighs and marinate for at least 20 minutes.

In a large bowl, combine the shredded cabbage and julienned carrots. In a separate bowl, mix mayonnaise, sugar, and a dash of rice vinegar, then pour over the cabbage mixture, tossing well. Refrigerate for at least 15 minutes.

Heat a skillet over medium-high heat, add marinated chicken, and cook for about 6-7 minutes per side until the internal temperature reaches 165°F (74°C). Let it rest before slicing.

In the same skillet, melt butter and toast the sandwich buns cut-side down until golden brown.

Assemble the sandwich by placing sliced chicken on the bottom half of each bun, topping with cabbage slaw, and finishing with the top bun.