Start by cutting the chicken thighs into bite-sized pieces.

In a bowl, whisk together soy sauce, mirin, brown sugar, garlic, and ginger.

Heat sesame oil in a large skillet over medium-high heat.

Add the chicken pieces, cooking until browned on all sides, about 5-7 minutes.

Pour the teriyaki sauce over the chicken and stir to coat evenly, bringing to a simmer.

In a small bowl, mix cornstarch and water to create a slurry.

Add this to the skillet to thicken the sauce, stirring constantly until desired consistency.

Continue cooking for another 2-3 minutes until the chicken is cooked through.

Remove from heat and transfer the teriyaki chicken to a serving dish.

Garnish with chopped green onions and serve over rice or noodles.