Place chicken in a bowl or zip-top bag with 1 cup cornstarch. Shake/toss well until evenly coated (press the cornstarch on for better adhesion). Shake off excess.

Heat 1–2 inches of oil in a wok or deep pan to 350–375°F (medium-high; use a thermometer if possible). Fry chicken in batches (don’t overcrowd) for 5–7 minutes until golden and crispy. Remove to a paper towel-lined plate or wire rack.

For extra crispiness (highly recommended): Let chicken rest 5 minutes, then fry a second time for 1–2 minutes until deeper golden. This creates craggy bits that hold sauce better without sogginess.

While chicken fries, whisk together sauce ingredients except garlic, ginger, red pepper flakes, and cornstarch slurry: broth, rice vinegar, hoisin, soy sauce, and sugar.

In the same pan (drain most oil, leave ~1 tbsp), sauté grated ginger, garlic, and red pepper flakes over medium-low heat for 30–60 seconds until fragrant (don’t burn).

Pour in the sauce mixture and bring to a simmer. Give the cornstarch slurry a quick whisk, then stir it in. Cook 2–4 minutes, stirring, until glossy and thickened to a nice coating consistency (it should coat the back of a spoon but still flow). Taste and adjust: more vinegar for tang, sugar for sweetness, or flakes for heat.

Add the fried chicken back to the pan. Toss gently but quickly to coat evenly in the sauce. Drizzle in the toasted sesame oil, give one final toss, and remove from heat immediately.

Serve right away over rice, garnished with sesame seeds and scallions. Add steamed or stir-fried broccoli on the side for a classic touch if desired.