In a dutch oven, heat 1 inch of oil to 350°F/180°C.
Season the chicken with salt and set aside.
In a bowl, whisk the egg with oil. In a shallow dish, combine the flour with the cornstarch. Now dip the chicken pieces in the egg mixture, then dredge in the flour mixture. Shake off any excess.
Add the breaded chicken pieces to the hot oil and fry for 3-4 minutes. Remove from the oil when the internal temperature of the chicken reaches 165°F/74°C. The chicken will be a little pale in color. Drain on a wire rack and keep in a warm oven as you fry the rest of the chicken.
In a bowl, combine all of the sauce ingredients except for the ginger and garlic.
To a pan, add 1 tablespoon of oil (you can use the same oil you used for frying) and sauté the garlic and ginger for 30 seconds. Add the sauce mixture, and bring it to a boil. Reduce the heat to simmer and cook until the sauce has thickened.
Remove the sauce from the heat, add the fried chicken pieces to the sauce, and mix until the chicken is well coated. Serve over rice, garnished with fresh chopped green onion.