Step 1: Marinate the Chicken

1. In a medium mixing bowl, combine the soy sauce, sesame oil, honey, gochujang, minced garlic, grated ginger, and black pepper. Whisk until well combined to form the marinade.
2. Add the chicken thighs to the bowl, ensuring each piece is fully coated in the marinade. Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, or up to 2 hours for maximum flavor.

Step 2: Cook the Rice

1. While the chicken is marinating, cook the rice according to the package instructions. Use a rice cooker, Instant Pot, or stovetop, depending on your preference.
2. Once cooked, fluff the rice with a fork and set it aside, keeping it warm.

Step 3: Prepare the Vegetables

1. Wash and slice the cucumber, carrot, radishes, and green onions. Set them aside for assembling the bowls.
2. If using spinach, blanch it briefly in boiling water (1-2 minutes) and then rinse with cold water. Squeeze out excess water and set aside.

Step 4: Cook the Chicken

1. Heat a large skillet or grill pan over medium-high heat. Add a drizzle of sesame oil or neutral cooking oil.
2. Remove the chicken from the marinade (discard any remaining marinade) and cook in the hot pan for 4-5 minutes on each side, or until the chicken is fully cooked and slightly caramelized. The internal temperature should reach 165°F (74°C).
3. Once cooked, transfer the chicken to a cutting board and let it rest for 5 minutes. Slice into thin strips.

Step 5: Make the Spicy Mayo (Optional)

1. In a small bowl, whisk together the mayonnaise, gochujang, sesame oil, and lime juice until smooth. Taste and adjust the spice level by adding more gochujang if desired.

Step 6: Assemble the Rice Bowls

1. Divide the cooked rice evenly among four serving bowls.
2. Top each bowl with sliced chicken, cucumber, carrot, radishes, spinach, and any additional toppings such as kimchi, avocado, or a fried egg.
3. Drizzle the spicy mayo over the bowls, or serve it on the side for dipping. Garnish with sesame seeds and sliced green onions.

Step 7: Serve and Enjoy

Serve the Korean Chicken Rice Bowls immediately while the chicken is warm. Offer extra gochujang or soy sauce on the side for those who want an extra kick of flavor.