Slice the chicken into 1-inch cubes and season with salt and baking soda. Let marinate in the fridge while you prep the other ingredients.
In a separate bowl, mix the sauce ingredients and combine well.
Heat oil in a sauté pan or wok on medium until hot. It should reach 350°F.
Coat the chicken with cornstarch and toss well.
Add pieces of chicken to the pan and turn the heat to medium-high. Fry for 3 minutes on one side, then flip each piece and cook them for 2 minutes more. Transfer to a plate.
In the same pan, sauté bell peppers, onion, and garlic for 1 minute. Add a pinch of salt and a splash of oil if needed.
Add the chicken back in and pour the black pepper sauce into the pan. Toss and coat evenly. Cook for about 1 minute or until the sauce thickens.
Turn off the heat and taste for seasonings. Serve hot over rice or rice noodles.