Pour oil into a wok until half full. Heat over medium-high heat until hot. Meanwhile, discard the skin from the duck. Peel the flesh from the bones and shred the meat. Set aside.
Deep-fry the wonton wrappers, 3–4 at a time, for 1–2 minutes each side or until golden. Remove to a wire rack to drain, once cool they will become crisp. Carefully pour the hot oil out of the wok, leaving 1 tablespoon oil in the wok.
Reheat the wok over medium-high heat. Add the mushrooms and stir-fry for 2 minutes until they start to soften. Add the duck, plum sauce and stir-fry paste. Stir-fry for 1–2 minutes or until well coated.
Place wontons wrappers on a platter, top with the warm duck mixture, cucumber and coriander. Serve.