01 - Whisk together miso paste, soy sauce, mirin, honey, sesame oil, garlic, ginger, rice vinegar, and black pepper in a large bowl until smooth.
02 - Add chicken thighs to the marinade, turning to coat thoroughly. Cover and refrigerate for at least 30 minutes (up to 4 hours for deeper flavor).
03 - Preheat oven to 400°F. Line a baking sheet with parchment paper or foil.
04 - Arrange marinated chicken thighs on the prepared baking sheet, shaking off excess marinade.
05 - Roast for 25–30 minutes, or until chicken is cooked through and caramelized at the edges.
06 - Transfer to a serving platter. Sprinkle with toasted sesame seeds and spring onions, if desired. Serve hot.