Heat deep fryer or vegetable oil in a wok to 180C.
Cut once and open up the tube so that the entire piece is flat on the cutting board, outside part facing up. Using a very sharp knife, score the entire surface of the squid in one direction, then rotate the squid and score again to form a criss-cross pattern. Be careful not to slice all the way through. Scoring the squid makes it tender. Now cut the squid into 8-10 pieces.
Pour iced water into a large bowl, add all the dry ingredients, then stir through lightly with a pair of chopsticks (no need to combine thoroughly until smooth).
Add all the squid pieces to the batter to coat, then carefully drop them into the oil one by one. Cook until golden brown and crisp before removing onto a wire rack to drain.
Plate the squid tempura, sprinkle with sea salt, spring onions and chilli. Serve immediately with ponzu dipping sauce.
