Cut 1 green onion/scallion diagonally into thin slices and set aside for garnish.
Cut 1 boneless, skinless chicken breast into small, bite-sized squares about 1½ inches (4 cm). Nami's Tip: I tilt my knife back and slice at an angle using the sogigiri cutting technique. This creates thinner, flatter pieces that cook evenly.
Place the chicken in a tray and season both sides with ¼ tsp Diamond Crystal kosher salt and ⅛ tsp freshly ground black pepper. Rub well.
Dust with 2–3 Tbsp potato starch or cornstarch and coat lightly. Dust off any excess starch.
To Cook the Chicken
Preheat a frying pan (I used a 10¼" carbon steel pan) on medium heat. When it's hot, add 2 Tbsp oil. When the oil is hot, add half the chicken in a single layer, leaving space between each piece. Leave untouched to sear for about 3 minutes.Nami's Tip: I cook in two batches to avoid crowding the pan. This helps to sear evenly and develop a nice crust.
Once the bottom develops a golden brown crust, flip to sear the other side for 2–3 minutes. When its brown and crispy on the bottom, transfer to a wire rack to drain the oil. Repeat with the next batch; if you're using a carbon steel pan like me, add an extra 1 Tbsp oil here; you won't need it if you're using a nonstick pan.Nami's Tip: Make sure that the chicken is cooked through after searing.
To Prepare the Glaze
Make a slurry by mixing ½ tsp potato starch or cornstarch and 1 tsp water in a small bowl. Set aside.
Add the sauce ingredients to a clean and cold pan: ¼ cup soy sauce, ¼ cup mirin, 2 tsp sugar, and 1 tsp sriracha sauce. Crush or mince 4 cloves garlic and add it to the pan.
Add 1 tsp toasted white sesame seeds. Turn on the stove to medium and heat the sauce until bubbling. Then, give the slurry a final stir and add it to the pan.
Stir constantly until the sauce thickens. It's done when you can draw a line through the sauce on the bottom of the pan with the spatula. Turn off and remove from the heat.
To Assemble
Transfer the cooked chicken to a large mixing bowl. Pour the hot glaze over the chicken.
Toss to coat well. Transfer to a serving plate. Garnish with sliced green onion and remaining toasted sesame seeds.
To Store
Transfer the leftovers to an airtight container and store in the fridge for up to 3 days or in the freezer for a month.