Chinese home cooks pressed for time often round out a meal with meats from the siu mei (roast meat) shop: anything from salt-baked chicken or roast duck to barbecued pork. While the roasts are delicious cut up and eaten plain, you can also use them as the base for another dish.
For this soup, buy half a roast duck from the siu mei shop (or your local supplier), but don't let the butcher cut it up. When you get it home, strip the meat in large pieces from the carcass. Use the carcass to make a flavourful broth for noodles, and top with the duck meat and some vegetables.
Strip the meat from the duck carcass.
Chop the carcass into several large pieces and place them in a medium-sized pot. Add 1.5 litres (1.5 quarts) of water, then place the pot over a medium-high flame. Bring to the boil then turn the flame to low and simmer, partially uncovered, for about 30 minutes.
Use a slotted ladle to remove the bones from the broth, then discard them. Taste the broth and add salt to the stock if necessary. Keep the stock hot over a very low flame.
While the broth is simmering, prepare the other ingredients. Put the rice noodles in a wide bowl, add warm water to cover and soak until pliable, about 15 minutes.
Neatly slice the duck meat. Cut the chillies (if using) into thin rounds, squeezing out and discarding the seeds as you go. Remove the tails and tips from the bean sprouts. Mince the spring onions.
Bring a pot of lightly salted water to the boil. Add the kale and boil until crisp tender, then use chopsticks to remove the vegetable and place them in a colander. Rinse with cold water, then place the kale on a plate.
Cook the noodles in the same pot of boiling water. Simmer until they are almost done, then add the bean sprouts, stir once, and strain through a colander.
Divide the noodles and bean sprouts between four bowls. Lay the duck meat and two or three kale stalks over each portion.
Ladle the hot broth on top, then add the chillies (if using). Drizzle a little sesame oil into each bowl and add the fresh coriander and spring onions. Serve immediately.