In a mixing bowl, whisk together miso paste, soy sauce (or tamari), honey, rice vinegar, sesame oil, garlic, and ginger until smooth.
Add chicken thighs to the bowl and toss until evenly coated with the marinade.
Cover and marinate for at least 30 minutes, or up to 4 hours for deeper flavor.
Preheat oven to 400°F (205°C). Line a baking dish or sheet pan with foil or parchment.
Arrange chicken thighs in a single layer, skin-side up if using skin-on thighs.
Bake uncovered for 35–40 minutes, until chicken is cooked through and the top is lightly caramelized.
Optional: Broil for 2–3 minutes at the end for extra color, watching closely to avoid burning.
Remove from oven and rest for 5 minutes before serving. Garnish if desired.