In a mixing bowl, combine the flour, cornstarch, salt, pepper, garlic powder, and onion powder.
In a separate bowl, beat the egg.
Dip each piece of chicken into the egg, then coat it in the flour mixture, ensuring an even coating.
Heat the vegetable oil in a frying pan over medium-high heat (or in a deep fryer) until the oil reaches 350°F (175°C).
Carefully add the coated chicken pieces to the hot oil in batches, avoiding overcrowding. Fry for 5-7 minutes or until golden brown and crispy. Use a slotted spoon or tongs to remove the chicken and place it on a paper towel-lined baking sheet to drain excess oil.
In a saucepan, combine the soy sauce, honey, mirin, ginger, garlic, and sesame oil. Cook over medium heat until the mixture begins to simmer.
Stir in the cornstarch-water mixture and continue to cook, stirring constantly, until the sauce thickens (about 1-2 minutes).
Toss the cooked chicken in the teriyaki sauce until well coated or serve the sauce drizzled on top of the chicken.