Once the oil heats up, add onions, bell pepper, and chicken to the skillet. Sauté the mixture, stirring occasionally, until the chicken is cooked through.
While the chicken is cooking, combine the peanut butter powder, water, brown sugar, soy sauce, and garlic chili sauce or sriracha sauce. Stir until well blended.
Add the garlic to the skillet and cook for one minute.
Drizzle the sauce over chicken and cook for about 1 minute.