Wash and finely dice the spring onions, reserving 4 long, narrow strips.
Cut the salmon into 4 pieces as square as possible. Halve the lime. Scatter the salmon with the spring onions and season with salt and pepper.
Juice the lime. For the dressing, mix together the lime juice, mustard and mango juice and season with salt and pepper.
Wash the rice paper sheets, one by one, in water.
Peel the carrots, clean the celery and cut both into fine julienned strips.
Put a piece of salmon on each rice paper sheet and fold up the dough to form a small parcel.
Tie each parcel with a strip of spring onion.
Place the parcels in a steamer and cook for 12-15 minutes.
Meanwhile, saute the vegetables in hot oil and cook for 5 minutes, stirring, until tender but not soft. Season with salt and pepper. Serve the fish parcels on the vegetables and drizzle with the dressing. Serve with soy sauce for dipping.