In a large bowl, combine the soy sauce, rice vinegar, brown sugar, minced garlic, grated ginger, and cornstarch. Add the boneless chicken thighs and ensure they are well coated. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.

Orange Sauce

Prepare the Orange Sauce

In a saucepan, combine the fresh orange juice, orange zest, soy sauce, honey, sesame oil, and red pepper flakes. Bring to a simmer over medium heat, stirring occasionally. Allow to cook for about 5-7 minutes until it thickens slightly. Set aside.

Frying the Chicken

Heat the Oil

In a large skillet or deep fryer, heat the vegetable oil over medium-high heat until it reaches 350°F (175°C).

Coat and Fry the Chicken

Remove the marinated chicken from the refrigerator. Dredge each piece in cornstarch, shaking off the excess. Carefully place the chicken in the hot oil, frying in batches if necessary to avoid overcrowding. Fry for about 5-6 minutes or until golden brown and cooked through. Use a slotted spoon to transfer the chicken to a paper towel-lined plate to drain excess oil.

Combining

Combine Chicken and Sauce

In a large bowl, toss the fried chicken pieces with the prepared orange sauce until well coated.

Garnishing

Garnish and Serve

Transfer the orange chicken to a serving platter. Sprinkle with chopped green onions and sesame seeds. Serve immediately with rice or noodles.