Cut chicken into bite size pieces. Season with salt and pepper.
In a medium bowl, whisk egg. Add cornstarch and whisk until smooth.
Heat up oil in a skillet. Dip each chicken pieces in cornstarch mixture, then fry in the pan on both sides. It does not have to cook through, just brown on each side. Repeat with each chicken pieces. It is better to do it in batches.
Place chicken in a 10" x 7" baking dish.
Preheat oven to 350 degrees F.
In a medium bowl, whisk together hot sauce, sugar, vinegar and salt.
Pour the sauce over chicken. Stir gently to make sure each piece is coated with sauce.
Bake for 30 minutes. The sauce will thicken and will be sticky.
Serve chicken over rice, garnished with chopped green onions and sprinkled with red pepper flakes.
Notes
Please note, that the nutrition value can vary depending on what product you use. The information below is an estimate. Always use calorie counter you are familiar with.
To make ahead: bake the chicken, then cool and store in the fridge for up to 4 days. The sauce will thicken even more during chilling so you may need to add a little bit of water during reheating.