Form the ground chicken into bite size chunks. Place the chicken chunks into a shallow vessel, spread apart so they are not mushing into one another. Pour the egg into the vessel so each chunk is coated.
Mix the flour and cornstarch in a shallow bowl. Heat the oil over medium heat to about 300°F.
Coat each chicken chunk well with the flour/cornstarch mixture. Fry each piece in the oil to an internal temperature of 160°F using a thermometer and until golden brown. Drain on a paper towel-lined plate to soak up any excess grease.
For the sauce: While the chicken is cooking, add the soy sauce, brown sugar, rice wine vinegar, sesame oil, garlic powder, and ginger to a saucepan. Bring to a simmer.
Dissolve the cornstarch in an equal amount of water. Pour into the simmering sauce until it becomes very thick. Remove from the heat and stir in the scallions.
Toss the chicken with the sauce. Garnish with sesame seeds and scallions.