In a bowl, combine sliced duck breast with cornstarch, Ponzu and sesame oil and toss to coat evenly and smooth out any lumps from the cornstarch.
Heat the oil in a medium-hot skillet or wok. Add the duck and liquid and quickly stir-fry for 1 minute. Add remaining ingredients and stir-fry for 2-3 minutes more.
Serve over warm American rice or noodles.