In a large bowl, whisk the egg, 2 tablespoons of cornstarch, salt and pepper.
Add in the chicken and toss until well coated.
Put 2 tablespoons of vegetable oil in a large skillet and place on medium-high heat.
Once oil is hot, add the chicken and all of the egg mixture.
Stirring occasionally, cook until chicken is cooked through and golden brown (about 7-10 minutes). Drain off any excess oil.
While the chicken is cooking, prepare the sauce.
In a small bowl, stir the soy sauce, water, sesame oil, brown sugar, rice vinegar, ginger, garlic, sesame seeds and cornstarch until well mixed.
Once chicken is done, and while the heat is still on, pour the sauce over the chicken and toss to coat well. The sauce should begin to thicken.
Once sauce reaches the desired consistency, turn off the heat.
Serve chicken with white or brown rice.