For the fish, scale, clean and fillet the sole (or you can get your fishmonger to do this for you). Clean the skeleton, then cut in half lengthways, keeping the backbone intact on one half. Discard the half of the skeleton without the back bone. Using a sharp knife, skin the sole fillets and cut each fillet into bite-sized pieces. Set aside.
Heat a deep fat fryer to 190C/375F. (CAUTION: hot oil can be dangerous - do not leave unattended.)
For the marinade and dipping sauce, place the green chilli, red chilli, ginger, garlic, coriander, sesame seeds, mustard, sesame oil, soy and lemon juice into a bowl and whisk to combine.
Heat the vegetable oil on high heat until smoking. Pour the hot oil into the bowl and stir - the sauce should splatter a little when the oil is added, so take care.
Pour half of the sauce into a shallow non-reactive dish and set the remainder aside. Place the sole pieces in with the sauce in the dish and leave to marinate for 15 minutes.
Meanwhile, dust the sole skeleton with a little of the potato starch.
Press the sole skeleton between a ladle and a metal bowl or second ladle to bend it, and carefully place into the hot oil to cook for 2-3 minutes. As it cooks and hardens, it should form a rough bowl shape. Remove the sole from the hot oil using a large slotted spoon. Drain on kitchen paper.
Lift the sole from the marinade and coat the pieces evenly in the remaining potato starch. Shake to remove any excess flour, then drop into the fat fryer and fry for 2-3 minutes, or until lightly golden-brown. Remove with a slotted spoon and drain on kitchen paper.
To serve, arrange the fish pieces on the curved sole skeleton using it as a serving bowl. Sprinkle with fresh lemon zest, yukari seasoning, fresh green chilli slices and coriander leaves. Serve with the little bowl of the dipping sauce.