1.Shell and devein prawns leaving heads and tails intact.
2.Combine prawns, sauces, juice, mirin and sugar in large bowl. Drain prawns; reserve ¼ cup marinade.
3.Heat half the oil in wok; stir-fry prawns, in batches, until changed in colour. Remove from wok.
4.Heat remaining oil in wok; stir-fry silver beet and capsicum until vegetables are tender. Return prawns to wok with reserved marinade and half the nori; stir-fry until mixture boils, season to taste. Serve sprinkled with remaining nori; accompany with lime.
Use sharp scissors to finely shred the nori. Prawn mixture can be marinated for a few hours or overnight in the fridge.