Learn how to make traditional Hakka abacus beads / abacus seeds (Suan Pan Zi) with a soft and slightly chewy texture that you can use for stir-fry later.
Cut tapioca into large chunks and steam over high heat until they are fork tender and can be easily mashed
Mash the taro while it's still hot. Add oil, salt, tapioca starch. Gradually add in the hot water and use a spoon to stir. It won't be thoroughly mixed. When the dough is not too hot to touch anymore, use your clean hands to knead it into a dough. If it's too sticky, you can add a little bit of tapioca flour until the dough comes together into a smooth dough and no longer sticky. If it's too dry, add a bit more hot water
Shaping into abacus beads:
Divide the dough into 4 equal balls. Work with one ball at a time while keeping the rest covered, roll the ball into long log (about 1-inch in diameter). Then cut into 1- 1.5 inch pieces. Roll each piece into a smaller ball. To make the round ones, use the end of a chopstick to make an indentation in the middle of the ball. To make a dis-like abacus, lightly flatten the ball with your palm, and then use your thumb to make an indentation in the middle of the disc. Continue with the rest of the dough until you are done
Boiling the abacus beads:
Bring a large pot of water to a boil. Add a pinch of salt and 1 Tbsp of cooking oil. Add in the abacus beads and stir a little bit, so they won't stick to together. They will float to the top once they are cooked. You can fish one out and have a try, it should be soft and chewy. Remove from the heat and drain off the water. Transfer to a bowl of cold water to stop the cooking process and to firm up the abacus beads. Toss with a little bit of oil to prevent them from sticking to each other
Stir-frying:
Preheat about 2 Tbsp of oil in a large wok or non-stick skillet. Add in the garlic and shallots and stir-fry until fragrant, about 30 seconds. Add dried shrimp and pork. Cook until the pork started to turn color, about 2 minutes. Add mushrooms and stir fry for another 30 seconds. Add abacus beads followed by seasonings. Stir to mix everything. Make sure the abacus beads are coated with the sauce. Add green onion stalks and mung bean sprouts the last (if using) and stir fry for another 30 seconds and turn off the heat to let residual heat soften the sprouts. Have a taste and add more fish sauce if needed. Remove from the heat into a serving platter and garnish with fried shallot crisp and serve immediately