In a medium bowl, combine the chicken pieces with soy sauce, rice vinegar, sesame oil, and 1 tablespoon of cornstarch. Let it marinate for at least 15 minutes.

In a separate bowl, whisk together the 0.5 cups of cornstarch and 0.5 cups of flour for the coating.

Heat vegetable oil in a large skillet or wok over medium-high heat.

Dredge the marinated chicken pieces in the cornstarch and flour mixture, ensuring they are fully coated, then carefully add them to the hot oil in batches to avoid overcrowding.

Fry chicken for 4-5 minutes per side, or until golden brown and cooked through, then remove and set aside on a wire rack.

In a small bowl, whisk together the chicken broth, soy sauce, hoisin sauce, rice vinegar, brown sugar, grated ginger, minced garlic, red pepper flakes, and 1 tablespoon of cornstarch to create the sauce.

Drain most of the oil from the skillet, leaving about 1 tablespoon, and add the sauce mixture.

Cook the sauce over medium heat, stirring constantly, until it thickens, about 2-3 minutes.

Add the cooked chicken to the thickened sauce and toss to coat evenly.

Garnish with sliced scallions and sesame seeds, then serve hot with rice.