1.Press tofu between 2 chopping boards with weight on top, raise one end; stand 25 minutes.
2.Meanwhile, combine dashi and the water in small saucepan. Add sake, mirin and sauce; bring to the boil. Remove from heat.
3.Cut tofu into 8 even-sized pieces; pat dry between layers of absorbent paper then toss in combined cornflour and sesame seeds. Heat oil in wok; deep-fry tofu, in batches, until browned lightly. Drain on absorbent paper.
4.Place 2 pieces of tofu in each serving bowl. Divide daikon, ginger and onion among bowls; pour dashi over tofu then sprinkle with bonito flakes.
Dashi is the basic fish and seaweed stock that accounts for the distinctive flavour of many Japanese dishes. It is made from dried bonito (mackerel) flakes and kombu (kelp). Instant dashi powder, also known as dashi-nomoto, can be purchased, from Asian grocery stores, in concentrated liquid or granule form; here, we used granulated dashi. Bonito flakes can be found in most Asian food stores.