For the Abacus Seeds:
500g peeled yam, cut into 1cm slices
150g tapioca starch
50g rice flour
3/4 teaspoon salt
3/4 teaspoon sugar
150-300ml hot water
1 dried squid, soaked in water until soft (at least 5 hours)
30g dried shrimp, soaked in water until soft (at least 5 hours)
120g minced pork
6 dried shiitake mushrooms, soaked in water until soft (at least 5 hours)
10g dried black fungus, soaked in water until soft (at least 5 hours)
4 cloves garlic, finely chopped
1 bunch Chinese celery, washed and cut into 1cm lengths
3 tablespoons vegetable oil
For the sauce:
2-3 tablespoons fish sauce
1 teaspoon dark soy sauce
1 teaspoon light soy sauce
2 tablespoons oyster sauce
1 teaspoon sugar
1 teaspoon sesame oil
1/2 teaspoon white pepper
350ml chicken stock or pork and anchovy stock
To make the abacus seeds, steam the yam slices for 15-20 minutes until they are very soft.
Transfer the hot yam to a large mixing bowl, and mash into a smooth paste. Add the tapioca starch, rice flour, salt and sugar and stir to combine roughly.
Drizzle a few tablespoons of hot water at a time, stirring to mix. When the dough starts to come together, add more water little by little. Once you have a cohesive dough, stop adding water.
When the dough is cool enough to handle, use your hands to knead it until smooth.
Pulling off small bits of dough, roll into a ball, then press between your thumb and index finger to create indentations on both sides. Set aside.
Bring a large pot of water to a rolling boil, and cook the abacus seeds in batches until they float. Drain them and rinse with cold water.
Drizzle with some neutral-flavoured oil to stop them sticking. Set aside.
Stir all the sauce ingredients together, using only 2 tablespoons of fish sauce to start with.
Clean the dried squid, and cut into thin slices. Using a pestle and mortar or food processor, break the dried squid up into a fine consistency.
Remove the stems of the shiitake mushrooms and slice the caps. Slice the black fungus thinly.
In a wok over medium-high heat, add the oil. Saute the minced pork until cooked through and separate. Add the garlic, then the dried squid strips and pounded dried shrimp.
Add the sliced shiitake mushrooms and black fungus, and fry everything until aromatic.
Pour the sauce in, and simmer everything for 5 minutes.
Add the abacus seeds to the wok, stirring and cooking for another 5 minutes, to allow the abacus to absorb the flavours of the sauce.