If you have whole Sichuan peppercorn, then grind 1 tablespoon of the peppercorns using a mortar and pestle or spice or coffee/grinder. Set aside.
Combine marinade ingredients in a small bowl and stir well.
Marinate the chicken in the marinade ingredients for about 30 minutes.
Add 3 tablespoon of the peanut oil to a wok or large skillet and set your stove to high. Once the oil is smoking (it needs to be hot!) add the chicken so that each piece has its own space on the wok/skillet and doesn't crowd each other. Leave it for a bit until it browns...it shouldn't take long. You will want to check to make sure it doesn't burn. Turn the pieces over and brown the other side. Once browned, remove the chicken and set aside.
Turn down the heat to medium and add remaining 2 tablespoon of peanut oil. When the heat is at medium, add the garlic, ginger, and scallions. Continuously stir for around a minute, and then add the whole dried chilies (or whole + snipped chilies). Stir until fragrant, about a minute or two.
Turn the heat up back to high, and quickly add your chicken. Stir to incorporate, and then add the sauce for the stir fry (be sure to mix this sauce well just before adding to the stir fry). Stir well and the dish will be ready in a couple of minutes or less!
Garnish with chopped and toasted peanuts if you desire!