Slice the chicken across the grain into ¼-inch thick tiles on an angle to make thin, ¼-inch planks. Place the chicken in a shallow bowl and add baking soda, salt, cornstarch, water and vegetable oil. Massage all the ingredients into the meat to combine. Set it aside until ready to use or you can cover and refrigerate for a few days.
Combine all sauce ingredients and set aside.
Heat the oil to medium high in a medium sauté pan and sauté the garlic until light brown. When you see the first wisps of white smoke, stir in the chicken and cook undisturbed for about 30 seconds. Stir and scrape the pan and cook for another 30 seconds. Stir in bell peppers, onion, red chilies and peanuts, and cook them for about 2 minutes until the onions start to turn translucent.
Add the sauce, stir constantly, and cook for an additional minute until the ingredients are piping hot and combined.