01 - Whisk together soy sauce, brown sugar, sesame oil, rice vinegar, gochujang, garlic, ginger, and black pepper in a bowl. Add chicken thighs and toss to coat thoroughly. Marinate for at least 15 minutes, or up to overnight in the refrigerator for optimal flavor penetration.
02 - Heat vegetable oil in a large grill pan or skillet over medium-high heat. Remove chicken from marinade, allowing excess to drip off. Cook chicken for 4 to 5 minutes per side until charred and cooked through, reaching an internal temperature of 165°F. Let rest for 5 minutes before slicing into strips.
03 - Divide cooked rice evenly among four serving bowls. Arrange sliced chicken, shredded carrots, cucumber slices, purple cabbage, and green onions on top of the rice. Sprinkle sesame seeds over each bowl as garnish.
04 - Finish with optional toppings such as kimchi, additional gochujang or sriracha, fresh lime wedges, or cilantro sprigs. Serve immediately while chicken is still warm.