01 - In a large mixing bowl, whisk together the 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, turning each piece to coat thoroughly. Cover and refrigerate for at least 30 minutes, or up to overnight for deeper flavor penetration.
03 - Preheat the oven to 400°F (200°C). 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. After the first 20 minutes, baste the thighs generously with the reserved marinade using a basting brush. Continue roasting until the internal temperature reaches 165°F (75°C) and the skin is golden and caramelized.
06 - While the chicken roasts, pour the remaining marinade into a small saucepan and bring to a boil over medium heat. For a thicker glaze, dissolve the cornstarch in water and stir into the boiling sauce. Simmer for 3 to 5 minutes, stirring occasionally, until the sauce is glossy and coats the back of a spoon.
07 - Transfer the roasted chicken thighs to a serving platter. Drizzle with the prepared teriyaki glaze and garnish with sliced green onions and toasted sesame seeds. Serve immediately while hot.