For the Ponzu Beef, first prepare the ponzu sauce. Combine soy sauce, mirin, rice wine vinegar, ginger, shallots, lemon and lime juice and zest in a bowl to infuse for 1 hour. Strain through a fine sieve lined with muslin and set aside until needed.
Place bonito flakes, nori sheets and dashi powder in a saucepan with 1 litre of water, over a high heat. Simmer for 45 minutes until reduced. Strain through a fine sieve lined with muslin. Combine with the strained ponzu sauce and set aside until needed.
Trim eye fillet, wrap in cling film and roll to form a tight cylinder. Secure ends and place in fridge to firm into shape.
For the Pickle, combine sugar, rice vinegar, bay leaf, cloves and 100ml water in a saucepan over medium heat and bring to simmer, stirring to dissolve sugar. Remove from heat and set aside to cool.
Add cucumber slices, daikon slices, oyster mushrooms, sesame oil, soy sauce and salt and pepper to taste to the pickling liquid and stir well to combine. Set aside for 10 minutes to pickle.
For the Yuzu Mayonnaise, combine egg yolk, rice wine vinegar and mustard in a stick blender canister or tall jug and blitz with a stick blender until thickened. Add in remaining ingredients and blend until combined. Season to taste and set aside in fridge until needed.
For the Pan Fried Shitake Mushrooms, place a large fry pan over medium heat. Add sesame oil and shitake mushrooms and fry for 4-5 minutes until golden.
Add soy sauce and salt and pepper to taste and cook until liquid evaporates. Remove from heat and set aside, keeping warm until needed to serve.
To finish the Ponzu Beef, place a large frypan on the stovetop over high heat. Remove beef fillet from fridge and, keeping the cling wrap on, slice into 2.5 cm rounds. Remove cling wrap from slices, drizzle each steak with oil and season to taste. Cook in hot frypan for 4 minutes on each side or until cooked to your liking. Remove from pan and set aside to rest for 2 minutes before serving
To serve, slice beef and drizzle with ponzu dashi sauce. Divide the beef evenly between 6 serving plates. Add pickled vegetables, shitakes and Yuzu Mayonnaise. Sprinkle with toasted sesame seeds.