Marinate the chicken with cornstarch (1 tablespoon), vegetable oil (1 tablespoon), soy sauce (3/4 cup), and sugar (3/4 cup) for about 10 minutes.

In a separate bowl, mix together flour (1 1/2 cups), cornstarch (1/2 cup), garlic (1/2 cup), green onion (1/4 cup), sesame oil (1 tablespoon), red chili flakes (1 teaspoon), white pepper (1/2 teaspoon), and salt (1/2 teaspoon).

Heat additional vegetable oil in a frying pan over medium heat.

Dredge the marinated chicken cubes in the flour mixture until well coated.

Fry the coated chicken in the hot oil until golden brown and crispy, about 10 minutes.

Drain on paper towels before serving.