In a small saucepan, whisk together all of the ingredients to make the sauce.
Bring sauce to a low simmer for about 10 minutes until lightly thickens and darkens. Stir occasionally. Remove sauce from heat.
In a large mixing bowl, add cubed chicken with cornstarch and mix to fully coat. Add whisked egg to the chicken and gently toss to combine. Sprinkle flour over chicken and gently toss to combine.
Add oil to a large nonstick skillet over medium heat. Once hot, carefully add chicken to the skillet. Gently spread chicken out into an even layer and let cook until bottom is golden.
Once the bottom of the chicken is golden, flip over, gently breaking pieces apart if stuck together. Cook for another 5-7 minutes until golden and chicken is cooked through to at least 165 degrees and juices run clear.
Carefully drain any excess grease from the skillet.
Pour sauce over chicken and gently toss to combine.
Serve General Tso's Chicken over steamed rice with fresh chopped green onions (optional).