Drain the tofu and then wrap it in paper towels and place in a strainer for 30 minutes to remove excess moisture. Cut the tofu into four pieces, dry again with paper towels, then coat with the potato starch.
Heat the oil to a suitable temperature for deep-frying (around 340 degrees). Carefully put the tofu pieces in to fry and when they turn golden, remove and drain on paper towels to remove excess oil.
In a small pan heat up the dashi stock, mirin, soy sauce, sugar and salt. Bring to the boil, ensuring that the sugar has dissolved.
Divide the tofu among four bowls. Pour a little of the hot broth into each bowl and garnish with the grated daikon, a dab of grated ginger, shiso, myoga, and green onion to taste.
This Agedashi Tofu recipe is meant to be enjoyed immediately. The broth can be saved for later, but once the tofu is fried it will not keep in the fridge.