Toss the chicken pieces in a mixing bowl with the cornstarch, white pepper and salt to coat. Set aside for 5 minutes.
Meanwhile, heat the oil to 350 degrees F in a wok over medium-high heat, or until a small cube of bread dropped into the oil floats and turns golden brown in 10 to 15 seconds. Add the chicken and cook, stirring frequently with a slotted spoon, until cooked through, about 5 minutes. Transfer to a paper-towel-lined plate to drain. Drain all but 1 tablespoon of the oil from the wok.
Return the wok to medium-high heat and the garlic, ginger and jalapenos and stir-fry briefly until softened, about 2 minutes. Add the peppercorns and dried chiles and toast, tossing continuously until fragrant and the chiles begin to blacken, about 30 seconds. Return the chicken to the wok, add the green peppers and toss until very hot and beginning to soften, about 2 minutes.
Pour in the vinegar and soy and toss until well combined. Add the chili oil and cook until heated through.
Transfer the chicken to a large shallow bowl, drizzle the sesame oil over the top and serve immediately.