Whisk together cornstarch, flour, and a pinch of salt in a medium bowl.

Beat the egg in a separate shallow dish.

Dip each chicken piece into the egg, then roll in the cornstarch-flour mix until thoroughly coated. Shake off excess.

Heat oil in a large skillet over medium-high heat until shimmering.

Fry the chicken in batches until golden brown and cooked through, about 3–4 minutes per side. Transfer cooked pieces to a paper towel-lined plate to drain.

In a clean pan over medium heat, combine honey, soy sauce, rice vinegar, Dijon mustard, and garlic powder. Stir and bring to a gentle simmer.

Reduce heat and let the sauce cook for 3–5 minutes until thickened slightly.

Add the fried chicken to the sauce, tossing quickly to coat.

Sprinkle with sesame seeds if using, and serve immediately with rice or vegetables.