1) Preheat the oven to 200℃,,.
2) Use a Nakiri knife to slice the vegetables. This is a Japanese-style vegetable knife and has a straight blade suitable for cutting all the way to the chopping board without the need for a horizontal pull or push like a typical western knife.
3) Cut the mushrooms into 1cm wide pieces. Peel the ginger and spring onions then shred them finely.
4) Combine all of the sauce ingredients into a small bowl.
5) Slice and skin the salmon into 4 fillets with a Japanese slicing knife, Yanagiba. Place each salmon fillet onto a sheet of foil or baking paper with a 1/2 tablespoon of vegetable oil. Remember that the paper has to be large enough to make a parcel later on.
6) Scatter the ginger, mushrooms and spring onion on top of the fish.
7) Make a parcel by folding the sides of the foil over the fish, then pour the sauce mixture over carefully, bringing the edges of the parcel together tightly to seal it. You can use string to tie the parcel if you use baking paper.
8) Place the parcels on a baking tray and bake for 15 minutes at 200℃,,.
9) To serve, open the parcel and place the fish fillet on the plate along with the Shichimi. Or you could leave the fish in the parcel, placing it directly on the plate.