Combine the first 7 ingredients in a medium bowl (does not have to be completely smooth). Heat the oil in a large wok or skillet set over medium-high heat. When hot, add chicken and stir-fry 4 minutes, until just cooked through and light golden. Lift the chicken out of the pan with a slotted spoon or with tongs and set on a plate.
Drain all but 1 Tbsp. of the remaining oil in the pan. Add the bell pepper and onion to the pan and cook 2 to 3 minutes. Add the peanut butter mixture and bring to a simmer. Return the chicken to the pan and cook and heat in the sauce 2 minutes.
To serve, let diners fill their own cabbage or lettuce leaves with the chicken mixture, cilantro, bean sprouts and peanuts, and then devour.