How to make it
Cut the duck breasts into thick slices 4 cm (1½ in) long x 1 cm (½ in) thick. Put the duck slices into a bowl and add the soy sauce, rice wine or dry sherry, sesame oil, salt, pepper and cornflour. Mix well and let the slices steep in the marinade for about 15 minutes.
Heat a wok or large frying-pan over high heat until it is very hot. Add the oil, and when it is very hot and slightly smoking, add the duck from the marinade and stir-fry for about 2 minutes. Remove the duck and drain it in a colander. The duck should be slightly pink. Pour off all but 1½ tablespoons of the oil and re-heat it over high heat, add the garlic and onion and stir-fry for 3 minutes or until the onions are brown and soft.
Turn the heat to low and add the oyster sauce, rice wine, chilli oil and sugar and stir for 2 minutes. Return the duck to the wok or pan. Stir to mix well, toss in the coriander sprigs and serve at once with plain rice.