Remove and discard the skin from the duck. Slice the duck into finger-sized strips and put into a bowl. Toss through the Chinese five spice and some seasoning. Set aside. Roughly chop the pak choi, keeping the stalks and leaves separate. Heat half the oil in a large frying pan or wok over high heat and stir-fry the duck for 5min. Empty into a bowl and set aside. Heat the remaining oil and fry the pak choi stalks, peppers and sugar snap peas for a few min, until they start to soften. Add ginger, pak choi leaves and chilli; fry for 1min. Return the duck to the pan with the black bean sauce and 100ml water. Heat through and check the seasoning. Sprinkle with coriander, if you like, and serve with rice.