Preheat oven to 190C/Gas 5.
1) Rip off 4 pieces of greaseproof paper to form packets each about 30-cm long. Season fish with salt and pepper. Place a piece of greaseproof paper in a shallow dish then in the centre of the paper stack 1/4 of the green onions and shiitakes, layer with slices of ginger and garlic and top with fish.
2) Combine the honey, vinegar and tamari and pour 1/4 of the sauce over fish. Fold over the top of the paper then roll the sides in to form a sealed pouch. Repeat with remaining paper and ingredients. Arrange the pouches on a baking tray and roast in hot oven 12 to 14 minutes.