In a small bowl, whisk together the cornstarch, egg, salt and pepper. Add the chicken cubes to the bowl and toss well to coat.
Whisk the sauce ingredients together in a bowl.
In a large skillet, heat up 1 tablespoon olive oil. Cook the chicken until it's golden on both sides, working in batches. Use the remaining 1 tablespoon of olive oil as needed.
Once the chicken is done, pour the sauce over the chicken and cook until it thickens.
Toss in the sesame seeds and mix.
Garnish with chopped scallions serve over rice.