To make Teriyaki
sauce, put soy sauce, Mirin and sugar in a non-stick pan and cook for 3 minutes or till the sauce thickens.
Take the fish fillets on
a plate, season them with salt and pepper. Brush with 1 tbsp oil.
Heat another non-stick
pan, add the fish fillets and cook for about 3 minutes on each side. Transfer onto a serving plate.
Add ½ tbsp oil to the
same pan and heat. Add mushrooms and cook for 2 minutes. Reduce heat, add the prepared Teriyaki sauce and mix. Simmer for 1 minute.
Pour this sauce over
the salmon fillets, garnish with spring onion and serve hot.