Place the eggs, salt and pepper in a bowl. Stir to combine.
Place the flour and 1/2 cup of cornstarch in a shallow bowl or on a plate. Stir to combine.
Dip each piece of chicken into the egg mixture, then into the flour. Repeat the process with all of the chicken.
Heat 3 inches of oil in a deep pan to 350 degrees F.
Add 7-8 pieces of chicken to the pan. Cook for 5 minutes or until crispy and golden brown. Repeat the process with the remaining chicken.
Drain the chicken on paper towels.
While the chicken is cooking, make the sauce. Place the lemon juice, sugar and water in a small saucepan and bring to a simmer.
Mix 1 tablespoon of cornstarch with 2 tablespoons of cold water. Pour the cornstarch mixture into the lemon juice mixture.
Bring the sauce to a boil. Cook, stirring constantly, for 1-2 minutes or until sauce has thickened.
Toss the lemon sauce with the chicken. Stir in the lemon zest. Sprinkle with sesame seeds and green onions, then serve immediately.