Add the egg, salt, pepper, and 1 tablespoon oil into a medium bowl and whisk to combine.
In a second bowl, add 1/2 cup cornstarch and flour, and stir to combine.
In a large deep skillet or a wok, add oil about 2 inches high and heat it to 375 degrees.
Dip chicken pieces in the egg mixture, then dredge in the flour mixture and fry the chicken in batches for 3 to 4 minutes or until golden, set aside on a wire rack.
To make the sauce combine all the sauce ingredients in a medium saucepan, stir and bring to a boil, cook until it thickens. Set aside.
Drain most of the oil from the pan where you cooked the chicken, leaving only about two tablespoons.
Add the string beans and bell pepper strips, and saute for 3-5 minutes, then add in the cooked chicken, sesame oil and the sauce, toss to combine.
Remove from heat and garnish with sesame seeds and chopped green onions before serving with rice.