1. Prepare the geoduck by removing the shell and stomach. Keep the geoduck shell for plating. Blanch the geoduck siphon and body meat in hot water for 10 seconds, and then drench in an ice bath. Separate the geoduck siphon from the body meat, and then remove the skin. Cut the geoduck siphon in half lengthwise.
2. Slice the cucumber and mango into small pieces, and mix with the ponzu sauce in a bowl. Set aside.
3. Thinly chop the daikon into long thin shreds. Set aside.
3. Clean the geoduck siphons with coarse sea salt and brush. Work at it and scrub until you feel some slime. Give the geoduck one more rinse in cold water.
4. Separate the cleaned geoduck siphons into two sections, horizontally down the middle. The geoduck siphon that is closer to the base of the neck (the thicker meat) will be for the Crudo. The geoduck closer to the tip of the siphon will be for sashimi.
3. For the sashimi: Slice the sashimi section into two parts (you should have four total). Score the cuts lightly lengthwise (vertically) in shallow slits. After scoring, slice the geoduck horizontally into long thin pieces.
5. For the Crudo: Score the geoduck lengthwise, a little bit deeper cuts than the sashimi scores. The geoduck should curl up after the deep scores. After scoring, slice the geoduck horizontally twice: the first slice to score it horizontally. The following incision to slice through the geoduck to create the piece long thin piece. This will create a double-cut to further enhance the texture of the geoduck Crudo.
6. To arrange: add the freshly cut daikon to the geoduck shells. Add the geoduck sashimi to one shell. Add the geoduck Crudo to the other shell. Finish the Crudo with ponzu, fresh cucumber, and mango. Enjoy!