In a large, shallow bowl, whisk together cornstarch, flour, salt, and black pepper.
Add beaten eggs to another bowl.
Pour about 2 inches of canola oil into a deep frying pan and heat it over medium-high heat.
Dip the chicken pieces into the beaten eggs.
Add the chicken chunks to the cornstarch mixture and toss until well-coated. Work in batches.
Cook it in batches in the hot oil until golden and crispy.
Remove to a plate and set aside.
Discard the oil and wipe the skillet clean.
Add all the Sauce ingredients to the same skillet and whisk to combine. Cook it over medium heat for 3-5 minutes until it starts to simmer.
Continue to cook for 5 minutes, until the mixture begins to thicken.
Once the sauce is thickened, add the chicken and stir to coat.
Remove from heat. Serve garnished with green onions and sesame seeds.