Prepare the teriyaki sauce: In a medium saucepan, combine the soy sauce (120ml or 1/2 cup), mirin (120ml or 1/2 cup), granulated sugar (80g or 1/3 cup + 1 tbsp), and water (60ml or 1/4 cup).

Heat the sauce mixture over medium heat, stirring occasionally, until the sugar is completely dissolved. Bring the mixture to a gentle simmer.

Reduce the heat to low and let the sauce simmer gently for about 5-7 minutes, allowing the flavors to meld and the sauce to slightly thicken. Do not boil vigorously.

While the sauce simmers, prepare the cornstarch slurry by mixing 1 tablespoon (15ml) of cornstarch with 2 tablespoons (30ml) of cold water in a small bowl until smooth. This will be used to thicken the sauce.

Slowly whisk the cornstarch slurry into the simmering teriyaki sauce. Continue to cook, stirring constantly, for another 1-2 minutes until the sauce has thickened to a syrupy consistency.

Remove the thickened teriyaki sauce from the heat and set it aside. You should have approximately 250-300ml (1 to 1 1/4 cups) of sauce.

Pat the chicken pieces dry with paper towels. This step is important for achieving a good sear and preventing the chicken from steaming.

Heat 2 tablespoons (30ml) of vegetable oil in a large skillet or wok over medium-high heat until shimmering. Do not overcrowd the pan; cook in batches if necessary.

Add the chicken pieces to the hot skillet in a single layer. Sear the chicken for about 3-4 minutes per side, until golden brown and cooked through. The internal temperature should reach 74°C (165°F).

Once the chicken is cooked, reduce the heat to medium-low. Pour the reserved teriyaki sauce over the chicken in the skillet. Toss to coat the chicken evenly.

Continue to cook for another 1-2 minutes, stirring gently, allowing the sauce to bubble and coat the chicken beautifully. The chicken should be glossy and well-glazed.

Serve the chicken teriyaki immediately over cooked rice. Garnish with toasted sesame seeds (1 tsp or 5ml) and thinly sliced green onions (2 stalks).