Step 1

Preheat the oven to 400F/200C.

Step 2

Trim the ends off the spring onions (both stem and dark green part) and peel off any rough outer layer. Cut them in to roughly 2-3 inch (5-7cm) pieces and slice them in half lengthwise. Cut the ginger in to thin slices and peel and slice the garlic.

Step 3

Line a baking dish big enough to hold the fish with a piece of foil that is big enough to wrap the fish with a bit of extra to fold together. Put roughly 1 onions-worth in a layer at the bottom of foil ad top with a couple slices of both garlic and ginger (see pictures above for this and next step).

Step 4

Make two cuts into either side of the fish then rest it on top of the onion, garlic and ginger slices. Put a couple more pieces of onion, ginger and garlic in the cavity then cut the last of the garlic and ginger in to smaller pieces to fit in the cut on the side of the fish. (Alternatively, just lay on top.) You should still have around 1 onion left.

Step 5

Mix together the soy sauce, sesame oil and rice vinegar and drizzle over the fish. Fold the foil over the fish and roll the edges together to seal up the packet.

Step 6

Place in the oven for around 25 minutes, or a little longer depending on the size and thickness of the fish, until the fish is cooked through. Serve topped with the remaining onion.