Partially fill a wok or saucepan with water (the base of the steamer should not touch the water) and bring to the boil.
Place a plate in the steamer or line with baking paper.
Arrange the mushrooms in the steamer and place the barramundi fillets on top of the mushrooms.
Combine the ginger, shoyu, lime juice, sesame oil and seeds in a bowl.
Place the steamer on top of the wok or saucepan, spoon the sauce over the fish, sprinkle with coriander and cover with the lid.
Steam for 10-12 minutes until the fish is opaque or flakes easily with a fork.
Remove steamer and serve barramundi fillets and mushrooms, spooning over any remaining sauce on the fish.