Add the soy sauce, mirin and white wine to a pan and reduce by half. Allow to cool.
Grind the coriander and mustard seeds with the Szechuan peppercorns, white peppercorns, ground ginger and mix together.
Roll the tuna loin in the ground spices, place into a preheated non stick pan with olive oil, cook on each side for 1 min. Remove and allow to rest.
Add the mango, cucumber, chives, mint and coriander to the reduced liquid.
Cook the pak choi in a little sesame oil. Place into the centre of the plate, slice the tuna on top then drizzle around the ponzu sauce. Dust with the crushed wasabi powder.
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