In a medium bowl, combine the beaten egg with 2 tablespoons of soy sauce. Add the chicken pieces and toss to coat thoroughly.
In a separate shallow dish, whisk together the flour and cornstarch. Dredge the chicken pieces in the flour mixture, shaking off any excess coating.
In a small mixing bowl, whisk together the remaining soy sauce, rice vinegar, sugar, chicken broth, and hoisin sauce to create the sauce base.
Heat vegetable oil in a wok or deep skillet to 375 degrees Fahrenheit.
Fry the chicken in small batches for 3 to 5 minutes until golden brown and the internal temperature reaches 165 degrees Fahrenheit. Drain on a wire rack.
Remove all but 1 tablespoon of oil from the wok. Sauté the minced ginger, garlic, and dried chilies over medium-high heat for 60 seconds until fragrant.
Pour the sauce base into the wok and bring to a vigorous simmer. Continue to cook until the sauce reduces and thickens into a glossy glaze.
Add the fried chicken pieces back into the wok. Toss rapidly to ensure even coating. Remove from heat and garnish with sliced green onions before serving.