01 - Whisk together soy sauce, brown sugar, sesame oil, garlic, ginger, gochujang, rice vinegar, sesame seeds, and black pepper in a bowl until well combined.
02 - Add chicken thighs to the marinade, turning to coat thoroughly. Cover and refrigerate for at least 30 minutes, up to 2 hours for deeper flavor penetration.
03 - While chicken marinates, shred the carrots and cabbage, slice the cucumber and avocado, and thinly slice the green onions. Cook rice if not already prepared.
04 - Combine mayonnaise, gochujang, rice vinegar, and honey in a small bowl. Mix until completely smooth and homogeneous. Set aside for serving.
05 - Heat a grill pan or skillet over medium-high heat. Cook marinated chicken thighs for 5-6 minutes per side until internal temperature reaches 165°F and exterior develops charred marks. Let rest for 5 minutes before slicing.
06 - Divide cooked rice evenly among four serving bowls. Arrange sliced BBQ chicken, shredded carrots, cucumber, purple cabbage, and avocado on top of rice.
07 - Drizzle generously with gochujang mayo, then sprinkle with sliced green onions and sesame seeds. Serve immediately while chicken is warm.