mirin, soybean paste, salt (Miso is food boiled and seasoned meeting well)
Boil some water in the pan. Add a pinch of salt. Boil xue choy quickly. Soak boiled xue choy into the cold water. Drain off. Cut into a little more than 1 inch length.
Wash sweet potato. Cut in round slices of 1/2 inch. Soak in water for 10 minutes.
Spread deep-fried tofu on the colander. Pour boiling water for remove excess oil. Cut into a bite pieces.
Put sweet potato and 5 or 6 dried small sardines. Pour 1 cup water and heat.
When water comes to boil, put xue choy and deep-fried tofu. Add 1 tablespoon mirin and soybean paste. Simmer with a small lid resting directly on the sweet potato for 5 minutes over low heat. Stop to heat and keep for 30 minutes.