In a medium bowl combine the chicken, 1/2 tsp baking soda, 2 tbsp fresh orange juice, 1 1/2 tbsp soy sauce, 1/2 tsp black pepper, 1 tbsp cornstarch, 1 tsp minced garlic, 1 tsp minced ginger and salt to taste; mix thoroughly and marinate at least 10 minutes.
In a separate bowl whisk together 1/3 cup fresh orange juice, 1 tbsp soy sauce, 1/4 cup rice vinegar, 1 1/2 tbsp chili garlic sauce (optional), 1/2 tbsp cornstarch, 2 tsp orange zest, 3 minced garlic cloves, 1 tsp minced ginger, 1/2 tsp red chili flakes, 3 tbsp brown sugar and salt to taste until the sugar and cornstarch are dissolved; set aside.
Heat a wide skillet over medium heat and add 1 tbsp oil.
Add the marinated chicken to the hot skillet in a single layer and cook 4–5 minutes without moving, then flip and cook another 5–6 minutes until cooked through.
Pour the prepared sauce into the skillet and cook uncovered, stirring occasionally, about 5 minutes until the sauce thickens and coats the chicken.
Stir in 1 tbsp sesame seeds and 2 tbsp chopped green onions, then remove from heat.
Serve the orange chicken with cooked rice and steamed broccoli.
