In a medium bowl, whisk together soy sauce, brown sugar, honey, minced garlic, and minced ginger until well combined.

Place the chicken thighs in a large resealable plastic bag or a shallow dish and pour the marinade over the chicken. Seal the bag or cover the dish and refrigerate for at least 1 hour, or up to overnight for more flavor.

Preheat your grill or a large skillet over medium-high heat. Remove the chicken from the marinade, reserving the marinade for later.

Cook the chicken on the grill or in the skillet for about 6-7 minutes per side, or until the internal temperature reaches 165°F.

While the chicken is cooking, pour the reserved marinade into a small saucepan. In a separate bowl, mix cornstarch and water until smooth, then add to the saucepan.

Bring the marinade to a boil over medium heat, stirring constantly until it thickens, about 2-3 minutes.

Once the chicken is cooked, remove it from the heat and let it rest for a few minutes before slicing.

Drizzle the thickened teriyaki sauce over the sliced chicken and garnish with sesame seeds and sliced green onions before serving.