Find the line running down the middle of the 400 grams boneless skinless chicken breast and separate it into two pieces.
400 grams boneless skinless chicken breast
Look for how the meat fibers run through the large piece of breast and cut it where the fibers change direction.
Now, you can cut each piece against the grain into ⅓-inch thick slices.
Add the chicken to a bowl with 1 tablespoon sake, ½ teaspoon grated ginger, and ⅛ teaspoon salt. Mix to combine. Add 2 teaspoons potato starch and work it in so each piece has an even coating of starch.
1 tablespoon sake, ½ teaspoon grated ginger, ⅛ teaspoon salt, 2 teaspoons potato starch
To make the teriyaki sauce, add 2 tablespoons sake, 1 tablespoon soy sauce, and 1 tablespoon sugar to a bowl and mix until the sugar has dissolved.
2 tablespoons sake, 1 tablespoon soy sauce, 1 tablespoon sugar
Heat a large frying pan over medium-high heat until hot. Add 1 tablespoon vegetable oil and chicken in a single layer, starting with the larger pieces.
1 tablespoon vegetable oil
When you're done adding the chicken, start flipping them over, starting with the pieces you added first.
When the chicken is mostly cooked (it doesn't need to be fully cooked), wipe out any excess oil with a paper towel and then add the teriyaki sauce.
Flip the teriyaki chicken pieces repeatedly until they're coated in a thick glaze.
Pack the teriyaki chicken into a bento box along with 1 batch cooked Japanese short-grain rice, and some side dishes.
1 batch cooked Japanese short-grain rice