In a medium saucepan, combine soy sauce and brown sugar. Heat over medium, stirring continuously until it begins to boil and thicken slightly, about 5 minutes. Stir in crushed garlic, chopped green onion, sesame oil, red chili flakes, and white pepper. Set aside to cool.

In a large mixing bowl, combine cubed chicken, cornstarch, and vegetable oil. Pour half of the prepared garlic sauce into the bowl, reserving the other half for later. Mix until well coated and marinate for at least 30 minutes.

Prepare the coating mixture by whisking together flour, cornstarch, and salt in a separate bowl. Mix in a few tablespoons of reserved garlic sauce until clumps form.

Heat enough vegetable oil in a deep frying pan or wok to cover the bottom by about 1 inch over medium-high heat until it reaches 350°F to 375°F.

Dredge the marinated chicken pieces in the prepared coating and fry in batches for about 3-4 minutes until golden brown and crispy.

Toss the fried chicken with the remaining warm garlic sauce, ensuring every piece is coated.