Whisk together the cornstarch, garlic powder, soy sauce, beer, and siracha in a small bowl. Add chicken to the marinade and toss to coat.
Whisk together the sauce ingredients in a small bowl and set aside.
Heat the oil in a large skillet or wok over medium-high heat until hot but not smoking. Add the minced garlic, cooking until fragrant, about 2 minutes. Add the bell peppers, stirring frequently until softened.
Add the chicken and marinade, cooking for about 5 minutes.
Pour in the sauce, reduce heat to maintain a simmer. Cook until the sauce has thickened and the chicken is cooked through for about 10-15 minutes.
Serve over cooked rice, topped with peanuts and green onion
Feel free to add veggies of your choice - celery, onion, broccoli, bok choy, carrots, baby corn, waterchestnuts, etc...