In a large saucepan, combine 1 1/2 cups water, orange juice, rice vinegar, soy sauce, and sesame oil. Blend well over medium-high heat for a few minutes.

Stir in the brown sugar, orange zest, ginger, garlic, and red pepper flakes, and bring it all to a boil.

In a small bowl, combine 3 tablespoons of cornstarch with 2 tablespoons of water and mix until smooth.

Slowly stir this cornstarch mixture into the sauce and let it simmer while stirring until it thickens. Keep the sauce warm on low heat.

Heat a Dutch oven with vegetable oil to 355°F (175°C).

In a mixing bowl, combine cornstarch, salt, and pepper.

Set up three bowls: one with beaten eggs, another with panko breadcrumbs, and the third with the cornstarch mixture.

Dip each piece of chicken in the egg mixture, dredge in cornstarch, dip again in the eggs, and finally coat with panko breadcrumbs.

In batches, fry the breaded chicken pieces in the hot oil until golden brown and fully cooked, approximately 4 minutes for each batch.

Once the chicken is crispy and golden, remove it from the oil and place it on paper towels to drain excess oil.

Pour the warm sauce over the crispy chicken and toss gently to coat. Garnish with chopped green onions.