Crack the egg into a large mixing bowl, whisk in 1 tablespoon soy sauce, then add the chicken pieces and toss to coat evenly.
In a shallow bowl combine 1 cup cornstarch, 1 cup all-purpose flour, 1/2 teaspoon garlic powder, 1/2 teaspoon baking powder, and 1/2 teaspoon salt.
Heat 1–2 inches of vegetable oil in a deep pan or Dutch oven to about 350°F (175°C).
Working in batches, transfer marinated chicken to the dry coating and press to adhere, shaking off excess. Fry in a single layer 4–5 minutes per batch until golden and cooked through. Drain on paper towels.
While chicken cooks, whisk together sauce ingredients in a medium bowl: 1/2 cup water, 1 tablespoon cornstarch, 1/4 cup soy sauce, 3 tablespoons honey, 2 tablespoons vinegar, 2 tablespoons brown sugar, 1 tablespoon sweet chili sauce or sriracha, and 1 tablespoon sesame oil until smooth.
Heat 1 teaspoon vegetable oil in a large skillet over medium heat. Sauté minced garlic and grated ginger (if using) about 1 minute, then pour in the sauce and cook 1–2 minutes until thickened.
Add the cooked fried chicken to the skillet, toss to coat in the sauce, sprinkle with sesame seeds, and serve immediately with rice or noodles if desired.