In a medium bowl, whisk together the soy sauce, brown sugar, honey, gochujang, rice vinegar, sesame oil, garlic, ginger, and sesame seeds until the sugar dissolves. Add the chicken thighs and toss well to coat. Let the chicken marinate at room temperature for at least 20 minutes, or refrigerate up to 2 hours for deeper flavor.

While the chicken marinates, prepare the slaw. In a large bowl, combine the shredded green cabbage, red cabbage, and grated carrot. In a small bowl, whisk together the mayonnaise, rice vinegar, sugar, salt, and pepper until smooth. Pour the dressing over the cabbage mixture and toss to coat evenly. Refrigerate until ready to serve—the crisp, tangy slaw balances the rich, spicy chicken beautifully.

Heat a cast-iron skillet or grill pan over medium-high heat. Lightly oil the pan if needed. Add the marinated chicken thighs in a single layer (work in batches if necessary) and cook for 6–7 minutes per side, until nicely charred and cooked through (internal temperature reaches 165°F). The sugars in the marinade will create a beautiful caramelized crust.

Transfer the cooked chicken to a cutting board and let rest for 5 minutes before slicing or leaving whole for the sandwiches.

Spread the cut sides of the buns with softened butter. Toast them on the skillet or under the broiler until golden and crisp on the edges. This step prevents sogginess and adds a rich, buttery texture.

Place the bottom bun halves on a work surface. Layer on the sliced or whole grilled chicken. Spoon on extra gochujang or Korean BBQ sauce if desired, then top with a generous handful of the chilled cabbage slaw. Crown with the top bun half and serve immediately while hot.