In a small bowl, stir together orange juice, soy sauce, sugar, and vinegar. Set aside.
In a medium bowl, add chicken; sprinkle with salt and 5 spice. Add cornstarch; toss to coat.
Heat vegetable oil in a large skillet or wok over medium-high heat.
Add half of chicken to pan; cook until browned on 1 side, about 6 minutes.
Turn chicken, and cook until browned, about 4 minutes more.
Transfer cooked chicken to a plate lined with paper towels. Repeat with remaining chicken.
Discard excess oil, if desired. Return all chicken to pan over medium-high heat; add sauce.
Cook and stir until sauce is thickened and chicken is coated, about 1 minute.
Sprinkle with sesame seeds and garnish with TK if desired.