01 - In a large bowl, whisk together soy sauce, mirin, honey, brown sugar, rice vinegar, minced garlic, grated ginger, and sesame oil until well combined.
02 - Add the chicken thighs to the bowl and turn to coat thoroughly on all sides. Cover and refrigerate for at least 30 minutes, or up to overnight for deeper flavor penetration.
03 - Preheat the oven to 400°F. Line a baking tray with parchment paper or aluminum foil for easier cleanup.
04 - Remove the chicken thighs from the marinade, reserving all the liquid. Place the thighs skin-side up on the prepared baking tray, spacing them evenly.
05 - Roast the chicken for 35 to 40 minutes, basting with the reserved marinade after the first 20 minutes. Continue roasting until the internal temperature reaches 165°F and the skin is golden brown and caramelized.
06 - While the chicken roasts, pour the remaining marinade into a small saucepan and bring to a boil. For a thicker glaze, dissolve the cornstarch in water and stir it into the sauce. Simmer for 3 to 5 minutes until glossy and thickened.
07 - Arrange the cooked chicken thighs on a serving platter. Drizzle generously with the prepared teriyaki glaze. Garnish with thinly sliced green onions and toasted sesame seeds. Serve immediately while hot.