In a mixing bowl, combine flour, cornflour, salt, and black pepper. Toss the chicken pieces in the flour mixture until well coated.

In a large skillet or wok, heat about ½ inch of oil over medium-high heat. Ensure the oil is hot before proceeding to the next step.

Carefully add the coated chicken pieces to the hot oil in batches, making sure not to overcrowd the pan. Fry for about 4-5 minutes or until golden brown and crispy, then transfer to a paper towel-lined plate to drain.

In a separate saucepan, combine orange juice, soy sauce, sugar, rice vinegar, minced garlic, and ginger paste. Bring it to a simmer over medium heat while stirring occasionally.

Once the sauce is simmering, let it cook for about 5-7 minutes until it slightly thickens.

Toss the crispy chicken in the sauce until fully coated, then serve hot. Garnish with sliced green onions and sesame seeds if desired.