MARINATE: Add the chicken to a medium bowl with the baking soda, ¼ teaspoon cornstarch, red pepper flakes, and 1 tablespoon of water. Stir and allow the chicken to marinate for at least 5 minutes (if you have time, 30 minutes is even better!)
SAUCE + BROCCOLI: in a mason jar with a tight-fitting lid, combine the soy sauce, seasoning sauce, 2 tablespoons cornstarch, oyster sauce, chicken stock, sesame oil, white pepper, and 2 tablespoons of water. Cover with a lid, and shake until combined. You should also add the broccoli to a microwave-safe bowl and steam (this usually takes 2.5-3 minutes.)
STIR FRY: Heat the oil in a large pan over medium-high heat. When the oil is hot, add the onions and give them 30 seconds to cook before adding the garlic. Stir and cook the garlic until it’s fragrant and golden. Then, add the chicken into the pan and cook the chicken until it browns evenly and cooks through; about 2-3 minutes. Add the steamed broccoli to the pan. Give the sauce one last shake in the jar before adding it into the pan. Continue to cook the sauce until it thickens, stirring occasionally so that the sauce doesn’t stick to the pan, about 1-2 minutes. Turn off the heat and serve with rice immediately.