Set up a breading station with two shallow bowls. In the first, place the beaten eggs. In the second, spread the cornstarch. Pat the chicken dry and season lightly with salt and pepper for extra flavor.
Dip each chicken piece into the egg, then coat thoroughly with the cornstarch. Shake off any excess so the pieces are evenly coated. This double-step helps you achieve a crisp, addictive crust.
Pour the oil into a deep skillet or a wide, heavy-bottomed pot to a depth of about 2 inches. Heat to 350°F (175°C). Fry the chicken in batches until golden and cooked through, about 3–4 minutes per batch. Use a slotted spoon to transfer the pieces to a paper-towel-lined rack and let drain.
Meanwhile, in a small saucepan, combine soy sauce, honey (or brown sugar), rice vinegar, sesame oil, garlic, ginger, ketchup (if using), and 1/4 cup water. Bring to a gentle simmer over medium heat, whisking to blend the flavors.
In a separate cup, stir the remaining 1/4 cup water with 1 tablespoon cornstarch to form a slurry. Pour this into the simmering sauce, whisking constantly until the mixture thickens into a glossy glaze.
Return the fried chicken to the pan with the sauce, tossing to coat each piece evenly. Allow the chicken to simmer in the glaze for 1–2 minutes so the sauce clings without becoming too thick or sticky.
Remove from heat and sprinkle with toasted sesame seeds. Finish with sliced scallions for a fresh, bright finish.
Serve hot over steamed rice or alongside crunchy stir-fried vegetables. The sauce should cling to every piece, creating a savory-sweet balance that lingers in your mouth.