For the five-spice duck, preheat the oven to 210C/410F/Gas 6.
Place the duck, skin-side up, on a rack over a roasting tray and pierce the skin all over with a knife.
Boil a kettle and pour the just boiled water over the duck skin. Discarding the water and pat the duck dry using kitchen paper. Rub salt, freshly ground black pepper and five-spice all over the skin.
Roast for 1-1¼ hours, or until crisp and golden-brown. Remove from the oven and set aside to rest for 10 minutes. Shred the duck into fine pieces using two forks.
Meanwhile, for the plum sauce, heat the olive oil in lidded pan and fry the spring onions for 1-2 minutes, or until softened. Add the spices and continue to cook for another 1-2 minutes.
Add the plums, vinegar and sugar and bring the mixture to the boil. Reduce the heat until the mixture is simmering, cover with a lid and simmer for 5-6 minutes, or until the plums are tender. Set aside to cool.
Remove the cinnamon stick and blend the mixture to a purée in a food processor. Strain the purée through a sieve into a bowl. Season, to taste, with salt and freshly ground black pepper.
For the pancakes, place the flour in a bowl and make a well in the centre. Pour in the boiling water and stir to form a dough. Tip the dough out onto a floured work surface and knead for 2-3 minutes, or until the dough is smooth.
Cut the dough into 16 pieces and roll each piece into a thin pancake.
Heat a frying pan until hot and fry each pancake for 1-2 minutes on each side, or until pale golden-brown. Keep the pancakes warm until ready to serve.
To serve, place the shredded duck on a large serving plate and place the spring onion and cucumber alongside. Place the pancakes on a separate serving plate and serve with the plum sauce.