Preheat oven to 425°F.
For the glaze, whisk together white miso, maple syrup, rice vinegar, sesame oil, and minced garlic. Thin with a splash of water if needed to get it brushable.
Pat thighs dry. Season with salt and black pepper.
Place thighs skin-side up on a sheet pan or in a cast iron. Roast for 25 minutes without touching them.
Pull the pan, brush the glaze generously over the skin. Return to oven for 5 minutes.
Repeat the glazing two more times, every 5 minutes.
Total cook time is around 40-45 minutes. Internal temp should hit 175°F in the thickest part.
Rest for 5 minutes. Finish with a scatter of sesame seeds and thinly sliced scallion if desired.