Add the Szechuan peppercorns to a skillet and toast on medium heat until fragrant, about 1-2 minutes. Crush the peppercorns using a mortar and pustule, bottom of a heavyweight glass or by pulsing in a spice grinder.
Whisk together all of the sauce ingredients in a small bowl. Set aside.
In a skillet over medium-high heat, add in the oil. Once warn, add in the chicken and cook, stirring occasionally until golden and cooked through, about 10 minutes. Remove the chicken from the skillet and set aside.
Add in the onion and bell peppers. Cook until just softened, about 3-5 minutes. Add in the garlic and chilis. Sautee for 1-2 minutes until fragrant.
Add the chicken and sauce into the skillet. Cook, stirring, until the sauce thickens, becomes glossy and coats the chicken. Serve over rice.
You can find Szechuan peppercorns at your local Asian market or online. They have a distinct flavor and cause your mouth to slightly tingle. If you must omit it, the recipe will still be delicious.
To adjust the spice level, increase, or decrease, the Chili Garlic Sauce and dried chilis.